--- a/dom/workers/ScriptLoader.cpp
+++ b/dom/workers/ScriptLoader.cpp
@@ -897,17 +897,19 @@ private:
     AssertIsOnMainThread();
     MOZ_ASSERT(aIndex < mLoadInfos.Length());
 
     WorkerPrivate* parentWorker = mWorkerPrivate->GetParent();
 
     nsIPrincipal* principal = mWorkerPrivate->GetPrincipal();
     nsCOMPtr<nsILoadGroup> loadGroup = mWorkerPrivate->GetLoadGroup();
     MOZ_DIAGNOSTIC_ASSERT(principal);
-    MOZ_ASSERT(NS_LoadGroupMatchesPrincipal(loadGroup, principal));
+
+    NS_ENSURE_TRUE(NS_LoadGroupMatchesPrincipal(loadGroup, principal),
+                   NS_ERROR_FAILURE);
 
     // Figure out our base URI.
     nsCOMPtr<nsIURI> baseURI = GetBaseURI(mIsMainScript, mWorkerPrivate);
 
     // May be null.
     nsCOMPtr<nsIDocument> parentDoc = mWorkerPrivate->GetDocument();
 
     nsCOMPtr<nsIChannel> channel;

--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -4793,16 +4793,17 @@ WorkerPrivate::GetLoadInfo(JSContext* aC
 
       // If we're called from a window then we can dig out the principal and URI
       // from the document.
       document = loadInfo.mWindow->GetExtantDoc();
       NS_ENSURE_TRUE(document, NS_ERROR_FAILURE);
 
       loadInfo.mBaseURI = document->GetDocBaseURI();
       loadInfo.mLoadGroup = document->GetDocumentLoadGroup();
+      NS_ENSURE_TRUE(loadInfo.mLoadGroup, NS_ERROR_FAILURE);
 
       // Use the document's NodePrincipal as our principal if we're not being
       // called from chrome.
       if (!loadInfo.mPrincipal) {
         loadInfo.mPrincipal = document->NodePrincipal();
         NS_ENSURE_TRUE(loadInfo.mPrincipal, NS_ERROR_FAILURE);
 
         // We use the document's base domain to limit the number of workers
@@ -4828,16 +4829,20 @@ WorkerPrivate::GetLoadInfo(JSContext* aC
           }
         } else {
           // Document creating the worker is not sandboxed.
           rv = loadInfo.mPrincipal->GetBaseDomain(loadInfo.mDomain);
           NS_ENSURE_SUCCESS(rv, rv);
         }
       }
 
+      NS_ENSURE_TRUE(NS_LoadGroupMatchesPrincipal(loadInfo.mLoadGroup,
+                                                  loadInfo.mPrincipal),
+                     NS_ERROR_FAILURE);
+
       nsCOMPtr<nsIPermissionManager> permMgr =
         do_GetService(NS_PERMISSIONMANAGER_CONTRACTID, &rv);
       NS_ENSURE_SUCCESS(rv, rv);
 
       uint32_t perm;
       rv = permMgr->TestPermissionFromPrincipal(loadInfo.mPrincipal, "systemXHR",
                                                 &perm);
       NS_ENSURE_SUCCESS(rv, rv);
@@ -4946,16 +4951,19 @@ WorkerPrivate::OverrideLoadInfoLoadGroup
   nsCOMPtr<nsILoadGroup> loadGroup =
     do_CreateInstance(NS_LOADGROUP_CONTRACTID);
 
   nsresult rv =
     loadGroup->SetNotificationCallbacks(aLoadInfo.mInterfaceRequestor);
   MOZ_ALWAYS_SUCCEEDS(rv);
 
   aLoadInfo.mLoadGroup = loadGroup.forget();
+
+  MOZ_ASSERT(NS_LoadGroupMatchesPrincipal(aLoadInfo.mLoadGroup,
+                                          aLoadInfo.mPrincipal));
 }
 
 void
 WorkerPrivate::DoRunLoop(JSContext* aCx)
 {
   AssertIsOnWorkerThread();
   MOZ_ASSERT(mThread);