diff --git a/src/commands/cmd_change_image_type.cpp b/src/commands/cmd_change_image_type.cpp
index a5567df1e..a24f5afb6 100644
--- a/src/commands/cmd_change_image_type.cpp
+++ b/src/commands/cmd_change_image_type.cpp
@@ -35,7 +35,6 @@ static bool cmd_change_image_type_enabled(const char *argument)
   const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
-    argument != NULL &&
     ((ustrcmp(argument, "rgb") == 0 && sprite->imgtype != IMAGE_RGB) ||
      (ustrcmp(argument, "grayscale") == 0 && sprite->imgtype != IMAGE_GRAYSCALE) ||
      (ustrncmp(argument, "indexed", 7) == 0 && sprite->imgtype != IMAGE_INDEXED));
diff --git a/src/commands/cmd_eyedropper_tool.cpp b/src/commands/cmd_eyedropper_tool.cpp
index 18422019e..26bc73972 100644
--- a/src/commands/cmd_eyedropper_tool.cpp
+++ b/src/commands/cmd_eyedropper_tool.cpp
@@ -55,7 +55,7 @@ static void cmd_eyedropper_tool_execute(const char *argument)
 
   if (color_type(color) != COLOR_TYPE_MASK) {
     /* set the color of the color-bar */
-    if (argument != NULL && ustrcmp(argument, "background") == 0)
+    if (ustrcmp(argument, "background") == 0)
       colorbar_set_bg_color(app_get_colorbar(), color);
     else
       colorbar_set_fg_color(app_get_colorbar(), color);
diff --git a/src/commands/cmd_flip.cpp b/src/commands/cmd_flip.cpp
index 5c709797d..be869b3a2 100644
--- a/src/commands/cmd_flip.cpp
+++ b/src/commands/cmd_flip.cpp
@@ -37,10 +37,10 @@
 
 static bool cmd_flip_enabled(const char *argument)
 {
+  assert(argument);
   const CurrentSpriteReader sprite;
   return
-    sprite != NULL &&
-    argument != NULL;
+    sprite != NULL;
 }
 
 static void cmd_flip_execute(const char *argument)
diff --git a/src/commands/cmd_open_file.cpp b/src/commands/cmd_open_file.cpp
index 545693c9a..f7b1f2836 100644
--- a/src/commands/cmd_open_file.cpp
+++ b/src/commands/cmd_open_file.cpp
@@ -145,13 +145,13 @@ static void cmd_open_file_execute(const char *argument)
   Console console;
   jstring filename;
 
-  /* interactive */
-  if (!argument) {
+  // interactive
+  if (ustrlen(argument) == 0) {
     char exts[4096];
     get_readable_extensions(exts, sizeof(exts));
     filename = ase_file_selector(_("Open Sprite"), "", exts);
   }
-  /* load the file specified in the argument */
+  // load the file specified in the argument
   else {
     filename = argument;
   }
diff --git a/src/commands/cmd_select_file.cpp b/src/commands/cmd_select_file.cpp
index 67e3630d8..022c04987 100644
--- a/src/commands/cmd_select_file.cpp
+++ b/src/commands/cmd_select_file.cpp
@@ -33,7 +33,7 @@
 static bool cmd_select_file_enabled(const char *argument)
 {
   /* with argument, the argument specified the ID of the GfxObj */
-  if (argument) {
+  if (ustrlen(argument) > 0) {
     int sprite_id = ustrtol(argument, NULL, 10);
     GfxObj *gfxobj = gfxobj_find(sprite_id);
     return gfxobj && gfxobj->type == GFXOBJ_SPRITE;
@@ -47,7 +47,7 @@ static bool cmd_select_file_checked(const char *argument)
 {
   const CurrentSpriteReader sprite;
 
-  if (argument) {
+  if (ustrlen(argument) > 0) {
     int sprite_id = ustrtol(argument, NULL, 10);
     GfxObj *gfxobj = gfxobj_find(sprite_id);
     return
@@ -62,7 +62,7 @@ static void cmd_select_file_execute(const char *argument)
 {
   UIContext* context = UIContext::instance();
 
-  if (argument) {
+  if (ustrlen(argument) > 0) {
     int sprite_id = ustrtol(argument, NULL, 10);
     GfxObj* gfxobj = gfxobj_find(sprite_id);
     assert(gfxobj != NULL);
diff --git a/src/widgets/editor/editor.cpp b/src/widgets/editor/editor.cpp
index 622f858c1..b24d0f2a0 100644
--- a/src/widgets/editor/editor.cpp
+++ b/src/widgets/editor/editor.cpp
@@ -1068,7 +1068,7 @@ static bool editor_msg_proc(JWidget widget, JMessage msg)
       else if (editor->alt_pressed) {
 	Command *command = command_get_by_name(CMD_EYEDROPPER_TOOL);
 	if (command_is_enabled(command, NULL))
-	  command_execute(command, msg->mouse.right ? "background": NULL);
+	  command_execute(command, msg->mouse.right ? "background": "");
 	return TRUE;
       }
       /* draw */