diff --git a/src/app/cmd/move_layer.h b/src/app/cmd/move_layer.h
index 8cae76f2d..6f73fc903 100644
--- a/src/app/cmd/move_layer.h
+++ b/src/app/cmd/move_layer.h
@@ -24,7 +24,7 @@ namespace cmd {
     void onExecute() override;
     void onUndo() override;
     void onFireNotifications() override;
-    size_t onMemSize() const {
+    size_t onMemSize() const override {
       return sizeof(*this);
     }
 
diff --git a/src/app/cmd/set_cel_frame.h b/src/app/cmd/set_cel_frame.h
index 6424e4603..a294f47c2 100644
--- a/src/app/cmd/set_cel_frame.h
+++ b/src/app/cmd/set_cel_frame.h
@@ -25,7 +25,7 @@ namespace cmd {
     void onExecute() override;
     void onUndo() override;
     void onFireNotifications() override;
-    size_t onMemSize() const {
+    size_t onMemSize() const override {
       return sizeof(*this);
     }
 
diff --git a/src/app/cmd/set_transparent_color.h b/src/app/cmd/set_transparent_color.h
index aaf7886b9..684739240 100644
--- a/src/app/cmd/set_transparent_color.h
+++ b/src/app/cmd/set_transparent_color.h
@@ -25,7 +25,7 @@ namespace cmd {
   protected:
     void onExecute() override;
     void onUndo() override;
-    void onFireNotifications();
+    void onFireNotifications() override;
     size_t onMemSize() const override {
       return sizeof(*this);
     }
diff --git a/src/app/commands/cmd_about.cpp b/src/app/commands/cmd_about.cpp
index e97a4337f..fc66933f3 100644
--- a/src/app/commands/cmd_about.cpp
+++ b/src/app/commands/cmd_about.cpp
@@ -24,7 +24,7 @@ public:
   Command* clone() const override { return new AboutCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 AboutCommand::AboutCommand()
diff --git a/src/app/commands/cmd_advanced_mode.cpp b/src/app/commands/cmd_advanced_mode.cpp
index 9d19cd0fa..9114cf3ba 100644
--- a/src/app/commands/cmd_advanced_mode.cpp
+++ b/src/app/commands/cmd_advanced_mode.cpp
@@ -30,7 +30,7 @@ public:
   Command* clone() const override { return new AdvancedModeCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 AdvancedModeCommand::AdvancedModeCommand()
diff --git a/src/app/commands/cmd_background_from_layer.cpp b/src/app/commands/cmd_background_from_layer.cpp
index cab35a82b..f78c9c6f9 100644
--- a/src/app/commands/cmd_background_from_layer.cpp
+++ b/src/app/commands/cmd_background_from_layer.cpp
@@ -26,8 +26,8 @@ public:
   Command* clone() const override { return new BackgroundFromLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 BackgroundFromLayerCommand::BackgroundFromLayerCommand()
diff --git a/src/app/commands/cmd_canvas_size.cpp b/src/app/commands/cmd_canvas_size.cpp
index f4055c1fb..ad3307e9b 100644
--- a/src/app/commands/cmd_canvas_size.cpp
+++ b/src/app/commands/cmd_canvas_size.cpp
@@ -274,8 +274,8 @@ public:
   Command* clone() const override { return new CanvasSizeCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 CanvasSizeCommand::CanvasSizeCommand()
diff --git a/src/app/commands/cmd_clear_cel.cpp b/src/app/commands/cmd_clear_cel.cpp
index aac85336f..21a84258b 100644
--- a/src/app/commands/cmd_clear_cel.cpp
+++ b/src/app/commands/cmd_clear_cel.cpp
@@ -30,8 +30,8 @@ public:
   Command* clone() const override { return new ClearCelCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ClearCelCommand::ClearCelCommand()
diff --git a/src/app/commands/cmd_copy_cel.cpp b/src/app/commands/cmd_copy_cel.cpp
index 7f661322d..a6f6366ec 100644
--- a/src/app/commands/cmd_copy_cel.cpp
+++ b/src/app/commands/cmd_copy_cel.cpp
@@ -24,8 +24,8 @@ public:
   Command* clone() const override { return new CopyCelCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 CopyCelCommand::CopyCelCommand()
diff --git a/src/app/commands/cmd_crop.cpp b/src/app/commands/cmd_crop.cpp
index a9e97ce0e..83904f7d4 100644
--- a/src/app/commands/cmd_crop.cpp
+++ b/src/app/commands/cmd_crop.cpp
@@ -88,8 +88,8 @@ public:
   Command* clone() const override { return new AutocropSpriteCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 AutocropSpriteCommand::AutocropSpriteCommand()
diff --git a/src/app/commands/cmd_deselect_mask.cpp b/src/app/commands/cmd_deselect_mask.cpp
index b6b0a5ad7..62e229c79 100644
--- a/src/app/commands/cmd_deselect_mask.cpp
+++ b/src/app/commands/cmd_deselect_mask.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new DeselectMaskCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 DeselectMaskCommand::DeselectMaskCommand()
diff --git a/src/app/commands/cmd_duplicate_layer.cpp b/src/app/commands/cmd_duplicate_layer.cpp
index 56344ca19..a2cf34193 100644
--- a/src/app/commands/cmd_duplicate_layer.cpp
+++ b/src/app/commands/cmd_duplicate_layer.cpp
@@ -31,8 +31,8 @@ public:
   Command* clone() const override { return new DuplicateLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 DuplicateLayerCommand::DuplicateLayerCommand()
diff --git a/src/app/commands/cmd_duplicate_sprite.cpp b/src/app/commands/cmd_duplicate_sprite.cpp
index 8c47c8369..c88ed4097 100644
--- a/src/app/commands/cmd_duplicate_sprite.cpp
+++ b/src/app/commands/cmd_duplicate_sprite.cpp
@@ -33,8 +33,8 @@ public:
   Command* clone() const override { return new DuplicateSpriteCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 DuplicateSpriteCommand::DuplicateSpriteCommand()
diff --git a/src/app/commands/cmd_exit.cpp b/src/app/commands/cmd_exit.cpp
index 174cfc8e5..fb8c3c9f8 100644
--- a/src/app/commands/cmd_exit.cpp
+++ b/src/app/commands/cmd_exit.cpp
@@ -24,7 +24,7 @@ public:
   Command* clone() const override { return new ExitCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 ExitCommand::ExitCommand()
diff --git a/src/app/commands/cmd_flatten_layers.cpp b/src/app/commands/cmd_flatten_layers.cpp
index 36a2bf1aa..02aa6f49f 100644
--- a/src/app/commands/cmd_flatten_layers.cpp
+++ b/src/app/commands/cmd_flatten_layers.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new FlattenLayersCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 FlattenLayersCommand::FlattenLayersCommand()
diff --git a/src/app/commands/cmd_fullscreen_preview.cpp b/src/app/commands/cmd_fullscreen_preview.cpp
index 8903f4f1b..3eac79ee7 100644
--- a/src/app/commands/cmd_fullscreen_preview.cpp
+++ b/src/app/commands/cmd_fullscreen_preview.cpp
@@ -257,8 +257,8 @@ public:
   Command* clone() const override { return new FullscreenPreviewCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 FullscreenPreviewCommand::FullscreenPreviewCommand()
diff --git a/src/app/commands/cmd_goto_layer.cpp b/src/app/commands/cmd_goto_layer.cpp
index 8909be088..bd27f7725 100644
--- a/src/app/commands/cmd_goto_layer.cpp
+++ b/src/app/commands/cmd_goto_layer.cpp
@@ -42,8 +42,8 @@ public:
   Command* clone() const override { return new GotoPreviousLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 GotoPreviousLayerCommand::GotoPreviousLayerCommand()
@@ -81,8 +81,8 @@ public:
   Command* clone() const override { return new GotoNextLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 GotoNextLayerCommand::GotoNextLayerCommand()
diff --git a/src/app/commands/cmd_invert_mask.cpp b/src/app/commands/cmd_invert_mask.cpp
index f904ed8e4..0d8377eaa 100644
--- a/src/app/commands/cmd_invert_mask.cpp
+++ b/src/app/commands/cmd_invert_mask.cpp
@@ -29,8 +29,8 @@ public:
   Command* clone() const override { return new InvertMaskCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 InvertMaskCommand::InvertMaskCommand()
diff --git a/src/app/commands/cmd_keyboard_shortcuts.cpp b/src/app/commands/cmd_keyboard_shortcuts.cpp
index 3cb578e47..a62c6fee0 100644
--- a/src/app/commands/cmd_keyboard_shortcuts.cpp
+++ b/src/app/commands/cmd_keyboard_shortcuts.cpp
@@ -446,7 +446,7 @@ public:
   Command* clone() const override { return new KeyboardShortcutsCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 KeyboardShortcutsCommand::KeyboardShortcutsCommand()
diff --git a/src/app/commands/cmd_layer_from_background.cpp b/src/app/commands/cmd_layer_from_background.cpp
index 19ff482fb..af7dcd713 100644
--- a/src/app/commands/cmd_layer_from_background.cpp
+++ b/src/app/commands/cmd_layer_from_background.cpp
@@ -26,8 +26,8 @@ public:
   Command* clone() const override { return new LayerFromBackgroundCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 LayerFromBackgroundCommand::LayerFromBackgroundCommand()
diff --git a/src/app/commands/cmd_mask_all.cpp b/src/app/commands/cmd_mask_all.cpp
index 76dad7850..e5776ceaa 100644
--- a/src/app/commands/cmd_mask_all.cpp
+++ b/src/app/commands/cmd_mask_all.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new MaskAllCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 MaskAllCommand::MaskAllCommand()
diff --git a/src/app/commands/cmd_mask_by_color.cpp b/src/app/commands/cmd_mask_by_color.cpp
index 39994a137..e981371ac 100644
--- a/src/app/commands/cmd_mask_by_color.cpp
+++ b/src/app/commands/cmd_mask_by_color.cpp
@@ -50,8 +50,8 @@ public:
   Command* clone() const override { return new MaskByColorCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 
 private:
   Mask* generateMask(const Sprite* sprite, const Image* image, int xpos, int ypos);
diff --git a/src/app/commands/cmd_mask_content.cpp b/src/app/commands/cmd_mask_content.cpp
index f9916bbcb..db652372d 100644
--- a/src/app/commands/cmd_mask_content.cpp
+++ b/src/app/commands/cmd_mask_content.cpp
@@ -34,8 +34,8 @@ public:
   Command* clone() const override { return new MaskContentCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 MaskContentCommand::MaskContentCommand()
diff --git a/src/app/commands/cmd_merge_down_layer.cpp b/src/app/commands/cmd_merge_down_layer.cpp
index 1269790aa..d97bd2dbc 100644
--- a/src/app/commands/cmd_merge_down_layer.cpp
+++ b/src/app/commands/cmd_merge_down_layer.cpp
@@ -38,8 +38,8 @@ public:
   Command* clone() const override { return new MergeDownLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 MergeDownLayerCommand::MergeDownLayerCommand()
diff --git a/src/app/commands/cmd_move_cel.cpp b/src/app/commands/cmd_move_cel.cpp
index 81bf2ae1b..ba212a69f 100644
--- a/src/app/commands/cmd_move_cel.cpp
+++ b/src/app/commands/cmd_move_cel.cpp
@@ -24,8 +24,8 @@ public:
   Command* clone() const override { return new MoveCelCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 MoveCelCommand::MoveCelCommand()
diff --git a/src/app/commands/cmd_new_file.cpp b/src/app/commands/cmd_new_file.cpp
index a1991f91a..6d8499e96 100644
--- a/src/app/commands/cmd_new_file.cpp
+++ b/src/app/commands/cmd_new_file.cpp
@@ -43,7 +43,7 @@ public:
   Command* clone() const override { return new NewFileCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 static int _sprite_counter = 0;
diff --git a/src/app/commands/cmd_new_layer_set.cpp b/src/app/commands/cmd_new_layer_set.cpp
index 9218a5624..7c4637203 100644
--- a/src/app/commands/cmd_new_layer_set.cpp
+++ b/src/app/commands/cmd_new_layer_set.cpp
@@ -33,8 +33,8 @@ public:
   Command* clone() const override { return new NewLayerSetCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 NewLayerSetCommand::NewLayerSetCommand()
diff --git a/src/app/commands/cmd_onionskin.cpp b/src/app/commands/cmd_onionskin.cpp
index 4362800b1..9612499e5 100644
--- a/src/app/commands/cmd_onionskin.cpp
+++ b/src/app/commands/cmd_onionskin.cpp
@@ -31,14 +31,12 @@ public:
   Command* clone() const override { return new ShowOnionSkinCommand(*this); }
 
 protected:
-  bool onChecked(Context* context)
-  {
+  bool onChecked(Context* context) override {
     DocumentPreferences& docPref = Preferences::instance().document(context->activeDocument());
     return docPref.onionskin.active();
   }
 
-  void onExecute(Context* context)
-  {
+  void onExecute(Context* context) override {
     DocumentPreferences& docPref = Preferences::instance().document(context->activeDocument());
     docPref.onionskin.active(!docPref.onionskin.active());
   }
diff --git a/src/app/commands/cmd_options.cpp b/src/app/commands/cmd_options.cpp
index 792715deb..b13be395e 100644
--- a/src/app/commands/cmd_options.cpp
+++ b/src/app/commands/cmd_options.cpp
@@ -390,7 +390,7 @@ public:
   Command* clone() const override { return new OptionsCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 OptionsCommand::OptionsCommand()
diff --git a/src/app/commands/cmd_play_animation.cpp b/src/app/commands/cmd_play_animation.cpp
index 7a18fcd15..b5178cde1 100644
--- a/src/app/commands/cmd_play_animation.cpp
+++ b/src/app/commands/cmd_play_animation.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new PlayAnimationCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 PlayAnimationCommand::PlayAnimationCommand()
diff --git a/src/app/commands/cmd_refresh.cpp b/src/app/commands/cmd_refresh.cpp
index b8c3e1e32..5d43ddacc 100644
--- a/src/app/commands/cmd_refresh.cpp
+++ b/src/app/commands/cmd_refresh.cpp
@@ -29,7 +29,7 @@ public:
   Command* clone() const override { return new RefreshCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 RefreshCommand::RefreshCommand()
diff --git a/src/app/commands/cmd_remove_frame.cpp b/src/app/commands/cmd_remove_frame.cpp
index 6507bdfcc..7b65ffbd3 100644
--- a/src/app/commands/cmd_remove_frame.cpp
+++ b/src/app/commands/cmd_remove_frame.cpp
@@ -28,8 +28,8 @@ public:
   Command* clone() const override { return new RemoveFrameCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 RemoveFrameCommand::RemoveFrameCommand()
diff --git a/src/app/commands/cmd_remove_layer.cpp b/src/app/commands/cmd_remove_layer.cpp
index 175054b20..79c292390 100644
--- a/src/app/commands/cmd_remove_layer.cpp
+++ b/src/app/commands/cmd_remove_layer.cpp
@@ -31,8 +31,8 @@ public:
   Command* clone() const override { return new RemoveLayerCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 RemoveLayerCommand::RemoveLayerCommand()
diff --git a/src/app/commands/cmd_reselect_mask.cpp b/src/app/commands/cmd_reselect_mask.cpp
index 74097db17..06d69ca3e 100644
--- a/src/app/commands/cmd_reselect_mask.cpp
+++ b/src/app/commands/cmd_reselect_mask.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new ReselectMaskCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ReselectMaskCommand::ReselectMaskCommand()
diff --git a/src/app/commands/cmd_reverse_frames.cpp b/src/app/commands/cmd_reverse_frames.cpp
index da468324f..34ebf43ce 100644
--- a/src/app/commands/cmd_reverse_frames.cpp
+++ b/src/app/commands/cmd_reverse_frames.cpp
@@ -25,8 +25,8 @@ public:
   Command* clone() const override { return new ReverseFramesCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ReverseFramesCommand::ReverseFramesCommand()
diff --git a/src/app/commands/cmd_save_file.cpp b/src/app/commands/cmd_save_file.cpp
index 90c62eca5..6fad7a4bc 100644
--- a/src/app/commands/cmd_save_file.cpp
+++ b/src/app/commands/cmd_save_file.cpp
@@ -254,7 +254,7 @@ public:
   Command* clone() const override { return new SaveFileCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 SaveFileCommand::SaveFileCommand()
@@ -292,7 +292,7 @@ public:
   Command* clone() const override { return new SaveFileAsCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 SaveFileAsCommand::SaveFileAsCommand()
@@ -311,7 +311,7 @@ public:
   Command* clone() const override { return new SaveFileCopyAsCommand(*this); }
 
 protected:
-  void onExecute(Context* context);
+  void onExecute(Context* context) override;
 };
 
 SaveFileCopyAsCommand::SaveFileCopyAsCommand()
diff --git a/src/app/commands/cmd_save_mask.cpp b/src/app/commands/cmd_save_mask.cpp
index 0275cb132..a01ba662a 100644
--- a/src/app/commands/cmd_save_mask.cpp
+++ b/src/app/commands/cmd_save_mask.cpp
@@ -27,8 +27,8 @@ public:
   Command* clone() const override { return new SaveMaskCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 SaveMaskCommand::SaveMaskCommand()
diff --git a/src/app/commands/cmd_sprite_properties.cpp b/src/app/commands/cmd_sprite_properties.cpp
index f20b38764..5d8f7d090 100644
--- a/src/app/commands/cmd_sprite_properties.cpp
+++ b/src/app/commands/cmd_sprite_properties.cpp
@@ -37,8 +37,8 @@ public:
   Command* clone() const override { return new SpritePropertiesCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 SpritePropertiesCommand::SpritePropertiesCommand()
diff --git a/src/app/commands/cmd_undo.cpp b/src/app/commands/cmd_undo.cpp
index e0d0ce1ef..12343b6cf 100644
--- a/src/app/commands/cmd_undo.cpp
+++ b/src/app/commands/cmd_undo.cpp
@@ -35,8 +35,8 @@ public:
   Command* clone() const override { return new UndoCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 
 private:
   Type m_type;
diff --git a/src/app/commands/cmd_unlink_cel.cpp b/src/app/commands/cmd_unlink_cel.cpp
index 47a8e6042..64dbf6ec8 100644
--- a/src/app/commands/cmd_unlink_cel.cpp
+++ b/src/app/commands/cmd_unlink_cel.cpp
@@ -30,8 +30,8 @@ public:
   Command* clone() const override { return new UnlinkCelCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 UnlinkCelCommand::UnlinkCelCommand()
diff --git a/src/app/commands/filters/cmd_color_curve.cpp b/src/app/commands/filters/cmd_color_curve.cpp
index 170dfa74e..23039beb3 100644
--- a/src/app/commands/filters/cmd_color_curve.cpp
+++ b/src/app/commands/filters/cmd_color_curve.cpp
@@ -81,8 +81,8 @@ public:
   Command* clone() const override { return new ColorCurveCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ColorCurveCommand::ColorCurveCommand()
diff --git a/src/app/commands/filters/cmd_convolution_matrix.cpp b/src/app/commands/filters/cmd_convolution_matrix.cpp
index 36749208b..0062183fc 100644
--- a/src/app/commands/filters/cmd_convolution_matrix.cpp
+++ b/src/app/commands/filters/cmd_convolution_matrix.cpp
@@ -149,8 +149,8 @@ public:
   Command* clone() const override { return new ConvolutionMatrixCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ConvolutionMatrixCommand::ConvolutionMatrixCommand()
diff --git a/src/app/commands/filters/cmd_despeckle.cpp b/src/app/commands/filters/cmd_despeckle.cpp
index 4bfc57993..fb865f84d 100644
--- a/src/app/commands/filters/cmd_despeckle.cpp
+++ b/src/app/commands/filters/cmd_despeckle.cpp
@@ -87,8 +87,8 @@ public:
   Command* clone() const override { return new DespeckleCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 DespeckleCommand::DespeckleCommand()
diff --git a/src/app/commands/filters/cmd_invert_color.cpp b/src/app/commands/filters/cmd_invert_color.cpp
index e73fc7237..c953f7129 100644
--- a/src/app/commands/filters/cmd_invert_color.cpp
+++ b/src/app/commands/filters/cmd_invert_color.cpp
@@ -48,8 +48,8 @@ public:
   Command* clone() const override { return new InvertColorCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 InvertColorCommand::InvertColorCommand()
diff --git a/src/app/commands/filters/cmd_replace_color.cpp b/src/app/commands/filters/cmd_replace_color.cpp
index f9b5a08a7..de6bcc550 100644
--- a/src/app/commands/filters/cmd_replace_color.cpp
+++ b/src/app/commands/filters/cmd_replace_color.cpp
@@ -116,8 +116,8 @@ public:
   Command* clone() const override { return new ReplaceColorCommand(*this); }
 
 protected:
-  bool onEnabled(Context* context);
-  void onExecute(Context* context);
+  bool onEnabled(Context* context) override;
+  void onExecute(Context* context) override;
 };
 
 ReplaceColorCommand::ReplaceColorCommand()
diff --git a/src/app/file/ase_format.cpp b/src/app/file/ase_format.cpp
index 1b77c3754..5d3d1e979 100644
--- a/src/app/file/ase_format.cpp
+++ b/src/app/file/ase_format.cpp
@@ -133,9 +133,9 @@ private:
 };
 
 class AseFormat : public FileFormat {
-  const char* onGetName() const { return "ase"; }
-  const char* onGetExtensions() const { return "ase,aseprite"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "ase"; }
+  const char* onGetExtensions() const override { return "ase,aseprite"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/bmp_format.cpp b/src/app/file/bmp_format.cpp
index 11ae684b0..f2352f661 100644
--- a/src/app/file/bmp_format.cpp
+++ b/src/app/file/bmp_format.cpp
@@ -44,9 +44,9 @@ class BmpFormat : public FileFormat {
     uint32_t blue_mask;         // Mask for blue channel.
   };
 
-  const char* onGetName() const { return "bmp"; }
-  const char* onGetExtensions() const { return "bmp"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "bmp"; }
+  const char* onGetExtensions() const override { return "bmp"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/fli_format.cpp b/src/app/file/fli_format.cpp
index 3631b024b..9a76ddfee 100644
--- a/src/app/file/fli_format.cpp
+++ b/src/app/file/fli_format.cpp
@@ -26,9 +26,9 @@ namespace app {
 using namespace base;
 
 class FliFormat : public FileFormat {
-  const char* onGetName() const { return "flc"; }
-  const char* onGetExtensions() const { return "flc,fli"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "flc"; }
+  const char* onGetExtensions() const  override{ return "flc,fli"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/gif_format.cpp b/src/app/file/gif_format.cpp
index ca2e8cbab..c1e742c75 100644
--- a/src/app/file/gif_format.cpp
+++ b/src/app/file/gif_format.cpp
@@ -62,9 +62,9 @@ enum class DisposalMethod {
 
 class GifFormat : public FileFormat {
 
-  const char* onGetName() const { return "gif"; }
-  const char* onGetExtensions() const { return "gif"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "gif"; }
+  const char* onGetExtensions() const override { return "gif"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
@@ -78,7 +78,7 @@ class GifFormat : public FileFormat {
       FILE_SUPPORT_GET_FORMAT_OPTIONS;
   }
 
-  bool onLoad(FileOp* fop);
+  bool onLoad(FileOp* fop) override;
 #ifdef ENABLE_SAVE
   bool onSave(FileOp* fop) override;
 #endif
diff --git a/src/app/file/ico_format.cpp b/src/app/file/ico_format.cpp
index 320233a81..6436dc886 100644
--- a/src/app/file/ico_format.cpp
+++ b/src/app/file/ico_format.cpp
@@ -25,9 +25,9 @@ namespace app {
 using namespace base;
 
 class IcoFormat : public FileFormat {
-  const char* onGetName() const { return "ico"; }
-  const char* onGetExtensions() const { return "ico"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "ico"; }
+  const char* onGetExtensions() const override { return "ico"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/jpeg_format.cpp b/src/app/file/jpeg_format.cpp
index cb6622c11..8c865d079 100644
--- a/src/app/file/jpeg_format.cpp
+++ b/src/app/file/jpeg_format.cpp
@@ -41,9 +41,9 @@ class JpegFormat : public FileFormat {
     float quality;              // 1.0 maximum quality.
   };
 
-  const char* onGetName() const { return "jpeg"; }
-  const char* onGetExtensions() const { return "jpeg,jpg"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "jpeg"; }
+  const char* onGetExtensions() const override { return "jpeg,jpg"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/pcx_format.cpp b/src/app/file/pcx_format.cpp
index 0a5daa040..2c63a3100 100644
--- a/src/app/file/pcx_format.cpp
+++ b/src/app/file/pcx_format.cpp
@@ -23,9 +23,9 @@ namespace app {
 using namespace base;
 
 class PcxFormat : public FileFormat {
-  const char* onGetName() const { return "pcx"; }
-  const char* onGetExtensions() const { return "pcx"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "pcx"; }
+  const char* onGetExtensions() const override { return "pcx"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/png_format.cpp b/src/app/file/png_format.cpp
index 971e0cd18..8c7e6c45e 100644
--- a/src/app/file/png_format.cpp
+++ b/src/app/file/png_format.cpp
@@ -28,9 +28,9 @@ namespace app {
 using namespace base;
 
 class PngFormat : public FileFormat {
-  const char* onGetName() const { return "png"; }
-  const char* onGetExtensions() const { return "png"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "png"; }
+  const char* onGetExtensions() const override { return "png"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/file/tga_format.cpp b/src/app/file/tga_format.cpp
index 4db1dd97f..38e4c219b 100644
--- a/src/app/file/tga_format.cpp
+++ b/src/app/file/tga_format.cpp
@@ -24,9 +24,9 @@ namespace app {
 using namespace base;
 
 class TgaFormat : public FileFormat {
-  const char* onGetName() const { return "tga"; }
-  const char* onGetExtensions() const { return "tga"; }
-  int onGetFlags() const {
+  const char* onGetName() const override { return "tga"; }
+  const char* onGetExtensions() const override { return "tga"; }
+  int onGetFlags() const override {
     return
       FILE_SUPPORT_LOAD |
       FILE_SUPPORT_SAVE |
diff --git a/src/app/tools/controllers.h b/src/app/tools/controllers.h
index 1e983b911..aa2487a04 100644
--- a/src/app/tools/controllers.h
+++ b/src/app/tools/controllers.h
@@ -78,7 +78,7 @@ private:
 // Controls clicks for tools like pencil
 class FreehandController : public Controller {
 public:
-  bool isFreehand() { return true; }
+  bool isFreehand() override { return true; }
 
   void pressButton(Points& points, const Point& point) override {
     points.push_back(point);
@@ -234,7 +234,7 @@ public:
     }
   }
 
-  void getPointsToInterwine(const Points& input, Points& output) {
+  void getPointsToInterwine(const Points& input, Points& output) override {
     ASSERT(input.size() >= 2);
     if (input.size() < 2)
       return;
@@ -243,7 +243,7 @@ public:
     output.push_back(input[1]);
   }
 
-  void getStatusBarText(const Points& points, std::string& text) {
+  void getStatusBarText(const Points& points, std::string& text) override {
     ASSERT(points.size() >= 2);
     if (points.size() < 2)
       return;
@@ -339,8 +339,8 @@ public:
 class OnePointController : public Controller {
 public:
   // Do not apply grid to "one point tools" (e.g. magic wand, flood fill, etc.)
-  bool canSnapToGrid() { return false; }
-  bool isOnePoint() { return true; }
+  bool canSnapToGrid() override { return false; }
+  bool isOnePoint() override { return true; }
 
   void pressButton(Points& points, const Point& point) override {
     if (points.size() == 0)
diff --git a/src/app/tools/inks.h b/src/app/tools/inks.h
index c0de6d35c..95aa4f4f4 100644
--- a/src/app/tools/inks.h
+++ b/src/app/tools/inks.h
@@ -34,10 +34,9 @@ public:
 
   Ink* clone() override { return new PaintInk(*this); }
 
-  bool isPaint() const { return true; }
+  bool isPaint() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     switch (m_type) {
 
       case Simple:
@@ -101,8 +100,7 @@ public:
     }
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     ASSERT(m_proc);
     (*m_proc)(x1, y, x2, loop);
   }
@@ -119,15 +117,13 @@ public:
 
   Ink* clone() override { return new ShadingInk(*this); }
 
-  bool isPaint() const { return true; }
+  bool isPaint() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     m_proc = ink_processing[INK_SHADING][MID(0, loop->sprite()->pixelFormat(), 2)];
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     (*m_proc)(x1, y, x2, loop);
   }
 
@@ -138,15 +134,13 @@ class ScrollInk : public Ink {
 public:
   Ink* clone() override { return new ScrollInk(*this); }
 
-  bool isScrollMovement() const { return true; }
+  bool isScrollMovement() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     // Do nothing
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     // Do nothing
   }
 
@@ -157,9 +151,9 @@ class ZoomInk : public Ink {
 public:
   Ink* clone() override { return new ZoomInk(*this); }
 
-  bool isZoom() const { return true; }
-  void prepareInk(ToolLoop* loop) { }
-  void inkHline(int x1, int y, int x2, ToolLoop* loop) { }
+  bool isZoom() const override { return true; }
+  void prepareInk(ToolLoop* loop) override { }
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override { }
 };
 
 
@@ -167,9 +161,9 @@ class MoveInk : public Ink {
 public:
   Ink* clone() override { return new MoveInk(*this); }
 
-  bool isCelMovement() const { return true; }
-  void prepareInk(ToolLoop* loop) { }
-  void inkHline(int x1, int y, int x2, ToolLoop* loop) { }
+  bool isCelMovement() const override { return true; }
+  void prepareInk(ToolLoop* loop) override { }
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override { }
 };
 
 
@@ -177,9 +171,9 @@ class SliceInk : public Ink {
 public:
   Ink* clone() override { return new SliceInk(*this); }
 
-  bool isSlice() const { return true; }
-  void prepareInk(ToolLoop* loop) { }
-  void inkHline(int x1, int y, int x2, ToolLoop* loop) {
+  bool isSlice() const override { return true; }
+  void prepareInk(ToolLoop* loop) override { }
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     // TODO show the selection-preview with a XOR color or something like that
     draw_hline(loop->getDstImage(), x1, y, x2, loop->getPrimaryColor());
   }
@@ -199,12 +193,11 @@ public:
 
   Ink* clone() override { return new EraserInk(*this); }
 
-  bool isPaint() const { return true; }
-  bool isEffect() const { return true; }
-  bool isEraser() const { return true; }
+  bool isPaint() const override { return true; }
+  bool isEffect() const override { return true; }
+  bool isEraser() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     switch (m_type) {
 
       case Eraser: {
@@ -251,8 +244,7 @@ public:
     }
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     (*m_proc)(x1, y, x2, loop);
   }
 };
@@ -264,21 +256,19 @@ class BlurInk : public Ink {
 public:
   Ink* clone() override { return new BlurInk(*this); }
 
-  bool isPaint() const { return true; }
-  bool isEffect() const { return true; }
-  bool needsSpecialSourceArea() const { return true; }
+  bool isPaint() const override { return true; }
+  bool isEffect() const override { return true; }
+  bool needsSpecialSourceArea() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     m_proc = ink_processing[INK_BLUR][MID(0, loop->sprite()->pixelFormat(), 2)];
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     (*m_proc)(x1, y, x2, loop);
   }
 
-  void createSpecialSourceArea(const gfx::Region& dirtyArea, gfx::Region& sourceArea) const {
+  void createSpecialSourceArea(const gfx::Region& dirtyArea, gfx::Region& sourceArea) const override {
     // We need one pixel more for each side, to use a 3x3 convolution matrix.
     for (const auto& rc : dirtyArea) {
       sourceArea.createUnion(sourceArea,
@@ -294,21 +284,19 @@ class JumbleInk : public Ink {
 public:
   Ink* clone() override { return new JumbleInk(*this); }
 
-  bool isPaint() const { return true; }
-  bool isEffect() const { return true; }
-  bool needsSpecialSourceArea() const { return true; }
+  bool isPaint() const override { return true; }
+  bool isEffect() const override { return true; }
+  bool needsSpecialSourceArea() const override { return true; }
 
-  void prepareInk(ToolLoop* loop)
-  {
+  void prepareInk(ToolLoop* loop) override {
     m_proc = ink_processing[INK_JUMBLE][MID(0, loop->sprite()->pixelFormat(), 2)];
   }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     (*m_proc)(x1, y, x2, loop);
   }
 
-  void createSpecialSourceArea(const gfx::Region& dirtyArea, gfx::Region& sourceArea) const {
+  void createSpecialSourceArea(const gfx::Region& dirtyArea, gfx::Region& sourceArea) const override {
     // We need one pixel more for each side.
     for (const auto& rc : dirtyArea) {
       sourceArea.createUnion(sourceArea,
@@ -329,10 +317,9 @@ public:
 
   Ink* clone() override { return new SelectionInk(*this); }
 
-  bool isSelection() const { return true; }
+  bool isSelection() const override { return true; }
 
-  void inkHline(int x1, int y, int x2, ToolLoop* loop)
-  {
+  void inkHline(int x1, int y, int x2, ToolLoop* loop) override {
     if (m_modify_selection) {
       Point offset = loop->getOffset();
 
@@ -355,8 +342,7 @@ public:
     }
   }
 
-  void setFinalStep(ToolLoop* loop, bool state)
-  {
+  void setFinalStep(ToolLoop* loop, bool state) override {
     m_modify_selection = state;
 
     if (state) {
diff --git a/src/app/ui/context_bar.cpp b/src/app/ui/context_bar.cpp
index eee24b7de..15a2b5c7a 100644
--- a/src/app/ui/context_bar.cpp
+++ b/src/app/ui/context_bar.cpp
@@ -490,7 +490,7 @@ private:
     getParent()->layout();
   }
 
-  bool onProcessMessage(ui::Message* msg) {
+  bool onProcessMessage(ui::Message* msg) override {
     if (msg->type() == kOpenMessage) {
       ColorBar::instance()->ChangeSelection.connect(
         Bind<void>(&InkShadesField::onChangeColorBarSelection, this));
diff --git a/src/app/ui/data_recovery_view.cpp b/src/app/ui/data_recovery_view.cpp
index 88b425c41..0adf89d87 100644
--- a/src/app/ui/data_recovery_view.cpp
+++ b/src/app/ui/data_recovery_view.cpp
@@ -58,7 +58,7 @@ public:
   Signal0<void> Regenerate;
 
 protected:
-  void onPreferredSize(PreferredSizeEvent& ev) {
+  void onPreferredSize(PreferredSizeEvent& ev) override {
     gfx::Size sz = m_deleteButton.getPreferredSize();
     sz.h += 4*guiscale();
     ev.setPreferredSize(sz);
diff --git a/src/app/ui/document_view.cpp b/src/app/ui/document_view.cpp
index 75c310703..6d767df1c 100644
--- a/src/app/ui/document_view.cpp
+++ b/src/app/ui/document_view.cpp
@@ -96,7 +96,7 @@ public:
       ->getCurrentQuicktool(currentTool);
   }
 
-  KeyAction getPressedKeyAction(KeyContext context) {
+  KeyAction getPressedKeyAction(KeyContext context) override {
     return KeyboardShortcuts::instance()->getCurrentActionModifiers(context);
   }
 
diff --git a/src/app/ui/editor/editor.cpp b/src/app/ui/editor/editor.cpp
index 7943d211a..b8a52368e 100644
--- a/src/app/ui/editor/editor.cpp
+++ b/src/app/ui/editor/editor.cpp
@@ -103,7 +103,7 @@ public:
     , m_g(g) {
   }
 
-  Editor* getEditor() {
+  Editor* getEditor() override {
     return m_editor;
   }
 
diff --git a/src/app/ui/editor/editor.h b/src/app/ui/editor/editor.h
index 9cebc924f..ee8caede9 100644
--- a/src/app/ui/editor/editor.h
+++ b/src/app/ui/editor/editor.h
@@ -220,7 +220,7 @@ namespace app {
     void onCurrentToolChange();
     void onFgColorChange();
     void onContextBarBrushChange();
-    void onExposeSpritePixels(doc::DocumentEvent& ev);
+    void onExposeSpritePixels(doc::DocumentEvent& ev) override;
 
   private:
     void setStateInternal(const EditorStatePtr& newState);