--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -6882,17 +6882,23 @@ nsWindow::GetCSDSupportLevel() {
             sCSDSupportLevel = CSD_SUPPORT_FLAT;
         } else if (strstr(currentDesktop, "Unity") != nullptr) {
             sCSDSupportLevel = CSD_SUPPORT_FLAT;
         } else if (strstr(currentDesktop, "Pantheon") != nullptr) {
             sCSDSupportLevel = CSD_SUPPORT_FULL;
         } else if (strstr(currentDesktop, "LXQt") != nullptr) {
             sCSDSupportLevel = CSD_SUPPORT_FULL;
         } else {
+// Release or beta builds are not supposed to be broken
+// so disable titlebar rendering on untested/unknown systems.
+#if defined(RELEASE_OR_BETA)
+            sCSDSupportLevel = CSD_SUPPORT_NONE;
+#else
             sCSDSupportLevel = CSD_SUPPORT_FLAT;
+#endif
         }
     } else {
         sCSDSupportLevel = CSD_SUPPORT_NONE;
     }
 
     // We don't support CSD_SUPPORT_FULL on Wayland
     if (!GDK_IS_X11_DISPLAY(gdk_display_get_default()) &&
         sCSDSupportLevel == CSD_SUPPORT_FULL) {