--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -3376,17 +3376,20 @@ XMLHttpRequestMainThread::OnRedirectVeri
     mErrorLoad = true;
   }
 
   mNewRedirectChannel = nullptr;
 
   mRedirectCallback->OnRedirectVerifyCallback(result);
   mRedirectCallback = nullptr;
 
-  return result;
+  // It's important that we return success here. If we return the result code
+  // that we were passed, JavaScript callers who cancel the redirect will wind
+  // up throwing an exception in the process.
+  return NS_OK;
 }
 
 /////////////////////////////////////////////////////
 // nsIProgressEventSink methods:
 //
 
 NS_IMETHODIMP
 XMLHttpRequestMainThread::OnProgress(nsIRequest *aRequest, nsISupports *aContext, int64_t aProgress, int64_t aProgressMax)