--- a/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
+++ b/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
@@ -111,16 +111,17 @@ nsTypeAheadFind::Init(nsIDocShell* aDocS
     return NS_ERROR_FAILURE;
 
   SetDocShell(aDocShell);
 
   if (!mDidAddObservers) {
     mDidAddObservers = true;
     // ----------- Listen to prefs ------------------
     nsresult rv = prefInternal->AddObserver("accessibility.browsewithcaret", this, true);
+    NS_ENSURE_SUCCESS(rv, rv);
     rv = prefInternal->AddObserver("accessibility.typeaheadfind", this, true);
     NS_ENSURE_SUCCESS(rv, rv);
 
     // ----------- Get initial preferences ----------
     PrefsReset();
 
     nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
     if (os) {