--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -7065,18 +7065,20 @@ nsWindow::GetCSDSupportLevel() {
         } else if (strstr(currentDesktop, "openbox") != nullptr) {
             sCSDSupportLevel = CSD_SUPPORT_FLAT;
         } else if (strstr(currentDesktop, "i3") != nullptr) {
             sCSDSupportLevel = CSD_SUPPORT_NONE;
         } else if (strstr(currentDesktop, "MATE") != nullptr) {
             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 {
-            sCSDSupportLevel = CSD_SUPPORT_NONE;
+            sCSDSupportLevel = CSD_SUPPORT_FLAT;
         }
     } 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) {