diff --git a/widget/gtk/WaylandSurface.cpp b/widget/gtk/WaylandSurface.cpp
--- a/widget/gtk/WaylandSurface.cpp
+++ b/widget/gtk/WaylandSurface.cpp
@@ -1043,13 +1043,15 @@
                                     RefPtr<WaylandBuffer> aWaylandBuffer) {
   LOGWAYLAND("WaylandSurface::DetachedLocked() WaylandBuffer [%p]",
              aWaylandBuffer.get());
   MOZ_DIAGNOSTIC_ASSERT(&aProofOfLock == mSurfaceLock);
 
-  bool removed =
-      CheckAndRemoveWaylandBuffer(aWaylandBuffer, /* aRemove */ true);
-  MOZ_DIAGNOSTIC_ASSERT(removed, "Wayland buffer is not attached?");
+  if (!CheckAndRemoveWaylandBuffer(aWaylandBuffer, /* aRemove */ true)) {
+    MOZ_DIAGNOSTIC_ASSERT(false, "Wayland buffer is not attached?");
+    NS_WARNING(
+        "WaylandSurface::DetachedLocked(): Wayland buffer is not attached?");
+  }
 }
 
 // Place this WaylandSurface above aLowerSurface
 void WaylandSurface::PlaceAboveLocked(const WaylandSurfaceLock& aProofOfLock,
                                       WaylandSurfaceLock& aLowerSurfaceLock) {