diff --git a/toolkit/components/antitracking/AntiTrackingCommon.cpp b/toolkit/components/antitracking/AntiTrackingCommon.cpp
index e7b8ab8f5f36..b90d31d86af7 100644
--- a/toolkit/components/antitracking/AntiTrackingCommon.cpp
+++ b/toolkit/components/antitracking/AntiTrackingCommon.cpp
@@ -65,7 +65,9 @@ GetParentPrincipalAndTrackingOrigin(nsGlobalWindowInner* a3rdPartyTrackingWindow
                                     nsIPrincipal** aTopLevelStoragePrincipal,
                                     nsACString& aTrackingOrigin)
 {
-  MOZ_ASSERT(nsContentUtils::IsTrackingResourceWindow(a3rdPartyTrackingWindow));
+  if (!nsContentUtils::IsTrackingResourceWindow(a3rdPartyTrackingWindow)) {
+    return false;
+  }
 
   nsIDocument* doc = a3rdPartyTrackingWindow->GetDocument();
   // Make sure storage access isn't disabled