diff --git a/intl/locale/LocaleService.cpp b/intl/locale/LocaleService.cpp
index 4ff18a1a90c4a..1527f2791037d 100644
--- a/intl/locale/LocaleService.cpp
+++ b/intl/locale/LocaleService.cpp
@@ -23,6 +23,9 @@
 #ifdef XP_WIN
 #  include "WinUtils.h"
 #endif
+#ifdef MOZ_WIDGET_GTK
+#  include "mozilla/WidgetUtilsGtk.h"
+#endif
 
 #define INTL_SYSTEM_LOCALES_CHANGED "intl:system-locales-changed"
 
@@ -69,6 +72,8 @@ static void ReadRequestedLocales(nsTArray<nsCString>& aRetVal) {
   const bool isRepack =
 #ifdef XP_WIN
       !mozilla::widget::WinUtils::HasPackageIdentity();
+#elif defined(MOZ_WIDGET_GTK)
+      !widget::IsRunningUnderSnap();
 #else
       true;
 #endif
diff --git a/toolkit/profile/xpcshell/head.js b/toolkit/profile/xpcshell/head.js
index 547489b5d8a22..12bcbe4a35c95 100644
--- a/toolkit/profile/xpcshell/head.js
+++ b/toolkit/profile/xpcshell/head.js
@@ -67,7 +67,7 @@ function simulateSnapEnvironment() {
   let env = Cc["@mozilla.org/process/environment;1"].getService(
     Ci.nsIEnvironment
   );
-  env.set("SNAP_NAME", AppConstants.MOZ_APP_NAME);
+  env.set("SNAP_INSTANCE_NAME", AppConstants.MOZ_APP_NAME);
 
   gIsLegacy = true;
 }
diff --git a/widget/gtk/WidgetUtilsGtk.cpp b/widget/gtk/WidgetUtilsGtk.cpp
index 21ae3863cdfb8..3e70c42973448 100644
--- a/widget/gtk/WidgetUtilsGtk.cpp
+++ b/widget/gtk/WidgetUtilsGtk.cpp
@@ -105,6 +105,8 @@ void SetLastMousePressEvent(GdkEvent* aEvent) {
   sLastMousePressEvent = event.release();
 }
 
+bool IsRunningUnderSnap() { return g_getenv("SNAP_INSTANCE_NAME") != nullptr; }
+
 bool IsRunningUnderFlatpak() {
   // https://gitlab.gnome.org/GNOME/gtk/-/blob/4300a5c609306ce77cbc8a3580c19201dccd8d13/gdk/gdk.c#L472
   static bool sRunning = [] {
diff --git a/widget/gtk/WidgetUtilsGtk.h b/widget/gtk/WidgetUtilsGtk.h
index 9d0109bd79eb3..bf9908fafa844 100644
--- a/widget/gtk/WidgetUtilsGtk.h
+++ b/widget/gtk/WidgetUtilsGtk.h
@@ -39,7 +39,7 @@ GdkEvent* GetLastMousePressEvent();
 
 // Return the snap's instance name, or null when not running as a snap.
 const char* GetSnapInstanceName();
-inline bool IsRunningUnderSnap() { return !!GetSnapInstanceName(); }
+bool IsRunningUnderSnap();
 bool IsRunningUnderFlatpak();
 inline bool IsRunningUnderFlatpakOrSnap() {
   return IsRunningUnderFlatpak() || IsRunningUnderSnap();