diff --git a/data/strings/en.ini b/data/strings/en.ini
index 3b3735720..2d70548d3 100644
--- a/data/strings/en.ini
+++ b/data/strings/en.ini
@@ -90,6 +90,7 @@ job_working = {0}<<Working...||&Cancel
 nothing_to_report = Crash Report<<Nothing to report||&OK
 install_extension = Warning\n<<Do you really want to install the given extension?\n<<"{0}"\n||&Install||&Cancel
 uninstall_extension_warning = Warning\n<<Do you really want to uninstall "{0}" extension?\n||&Yes||&No
+cannot_install_default_extension = Error<<This extension cannot be installed because tries to replace the default theme.<<Contact the developer so they fix the theme ID or theme name string<<from \"default\" to something else.||&OK
 unknown_output_file_format_error = Aseprite\n<<Unknown file format "{0}" in output filename\n||&OK
 update_screen_ui_scaling_with_theme_values = Update Screen/UI Scaling\n<<The new theme "{0}" wants to adjust some values for you:\n<<  Screen Scaling: {1}% -> {2}%\n<<  UI Scaling: {3}% -> {4}%\n<<Allow these changes?\n||&Adjust Scaling||&Don't Adjust Scaling
 update_extension = Update Extension\n<<The extension "{0}" already exists.\n<<Do you want to {1} from v{2} to v{3}?\n||&Yes||&No
diff --git a/src/app/commands/cmd_options.cpp b/src/app/commands/cmd_options.cpp
index b5ca06826..8db84fecf 100644
--- a/src/app/commands/cmd_options.cpp
+++ b/src/app/commands/cmd_options.cpp
@@ -926,6 +926,17 @@ public:
       }
     }
 
+    // Get the extension information from the compressed
+    // package.json file.
+    const ExtensionInfo info =
+      App::instance()->extensions().getCompressedExtensionInfo(filename);
+    // Check if the filename corresponds to aseprite-default theme
+    if (base::string_to_lower(info.name) ==
+        Extension::kAsepriteDefaultThemeExtensionName) {
+      ui::Alert::show(Strings::alerts_cannot_install_default_extension());
+      return false;
+    }
+
     // Install?
     if (ui::Alert::show(Strings::alerts_install_extension(filename)) != 1)
       return false;
@@ -1378,7 +1389,8 @@ private:
       if (!ext->isEnabled())
         continue;
 
-      if (ext->themes().empty())
+      if (ext->themes().empty() ||
+          isExtensionADuplicatedDefaultTheme(ext))
         continue;
 
       if (first) {
@@ -1410,6 +1422,9 @@ private:
     extensionsList()->addChild(sep);
     for (auto e : App::instance()->extensions()) {
       if (e->category() == category) {
+        if (category == Extension::Category::Themes &&
+            isExtensionADuplicatedDefaultTheme(e))
+          continue;
         ExtensionItem* item = new ExtensionItem(e);
         extensionsList()->addChild(item);
         hasItems = true;
@@ -1571,6 +1586,10 @@ private:
       // package.json file.
       ExtensionInfo info = exts.getCompressedExtensionInfo(filename);
 
+      if (info.defaultTheme) {
+        ui::Alert::show(Strings::alerts_cannot_install_default_extension());
+        return;
+      }
       // Check if the extension already exist
       for (auto ext : exts) {
         if (base::string_to_lower(ext->name()) !=
@@ -1749,6 +1768,17 @@ private:
     return paths;
   }
 
+  static base::paths getUserDirPaths(const base::paths& dirNames) {
+    ResourceFinder rf;
+    for (auto& fn : dirNames)
+      rf.includeUserDir(fn.c_str());
+
+    base::paths paths;
+    while (rf.next())
+      paths.push_back(base::normalize_path(rf.filename()));
+    return paths;
+  }
+
   void updateCategoryVisibility() {
     bool visibleCategories[int(Extension::Category::Max)];
     for (auto& v : visibleCategories)
@@ -1764,6 +1794,20 @@ private:
     }
   }
 
+  // Function to determine if the input extension is the default theme
+  static bool isExtensionADuplicatedDefaultTheme(const Extension* e) {
+    if (!e->isDefaultTheme())
+      return false;
+    auto userThemePaths =
+      getUserDirPaths({"extensions", skin::SkinTheme::kThemesFolderName});
+    for (auto& p : userThemePaths) {
+      // Has the user path (p) the same path of the extension (e->path())?
+      if (std::strncmp(e->path().c_str(), p.c_str(), p.size()) == 0)
+        return true;
+    }
+    return false;
+  }
+
 #ifdef LAF_WINDOWS
   void onTabletAPIChange() {
     const bool pointerApi = tabletApiWindowsPointer()->isSelected();
diff --git a/src/app/extensions.cpp b/src/app/extensions.cpp
index 768a9435e..6b6a1d5b2 100644
--- a/src/app/extensions.cpp
+++ b/src/app/extensions.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2020-2023  Igara Studio S.A.
+// Copyright (C) 2020-2024  Igara Studio S.A.
 // Copyright (C) 2017-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -51,12 +51,14 @@
 
 namespace app {
 
+const char* Extension::kAsepriteDefaultThemeExtensionName = "aseprite-theme";
+const char* Extension::kAsepriteDefaultThemeId = "default";
+
 namespace {
 
 const char* kPackageJson = "package.json";
 const char* kInfoJson = "__info.json";
 const char* kPrefLua = "__pref.lua";
-const char* kAsepriteDefaultThemeExtensionName = "aseprite-theme";
 
 class ReadArchive {
 public:
@@ -283,6 +285,8 @@ void Extension::addTheme(const std::string& id,
                          const std::string& path,
                          const std::string& variant)
 {
+  if (id == kAsepriteDefaultThemeId && !isDefaultTheme())
+    return;
   m_themes[id] = ThemeInfo(path, variant);
   updateCategory(Category::Themes);
 }
@@ -1003,6 +1007,21 @@ ExtensionInfo Extensions::getCompressedExtensionInfo(const std::string& zipFn)
     std::string err;
     auto json = json11::Json::parse(out.str(), err);
     if (err.empty()) {
+      if (json["contributes"].is_object()) {
+        auto themes = json["contributes"]["themes"];
+        if (json["name"].string_value() == Extension::kAsepriteDefaultThemeExtensionName)
+          info.defaultTheme = true;
+        else {
+          if (themes.is_array()) {
+            for (int i = 0; i < themes.array_items().size(); i++) {
+              if (themes[i]["id"].string_value() == Extension::kAsepriteDefaultThemeId) {
+                info.defaultTheme = true;
+                break;
+              }
+            }
+          }
+        }
+      }
       info.name = json["name"].string_value();
       info.version = json["version"].string_value();
       info.dstPath = base::join_path(m_userExtensionsPath, info.name);
diff --git a/src/app/extensions.h b/src/app/extensions.h
index 072ecfbd6..152170142 100644
--- a/src/app/extensions.h
+++ b/src/app/extensions.h
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2020-2023  Igara Studio S.A.
+// Copyright (C) 2020-2024  Igara Studio S.A.
 // Copyright (C) 2017-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -34,6 +34,7 @@ namespace app {
     std::string version;
     std::string dstPath;
     std::string commonPath;
+    bool defaultTheme = false;
   };
 
   enum DeletePluginPref { kNo, kYes };
@@ -41,6 +42,8 @@ namespace app {
   class Extension {
     friend class Extensions;
   public:
+    static const char* kAsepriteDefaultThemeExtensionName;
+    static const char* kAsepriteDefaultThemeId;
 
     enum class Category {
       None,
@@ -54,6 +57,8 @@ namespace app {
       Max
     };
 
+    bool isDefaultTheme() const;
+
     class DitheringMatrixInfo {
     public:
       DitheringMatrixInfo();
@@ -150,7 +155,6 @@ namespace app {
     void uninstall(const DeletePluginPref delPref);
     void uninstallFiles(const std::string& path,
                         const DeletePluginPref delPref);
-    bool isDefaultTheme() const;
     void updateCategory(const Category newCategory);
 #ifdef ENABLE_SCRIPTING
     void initScripts();