diff --git a/mozilla/toolkit/components/url-classifier/src/nsUrlClassifierDBService.cpp b/mozilla/toolkit/components/url-classifier/src/nsUrlClassifierDBService.cpp
index 5ed9cebbb8d..17b27c7f7bd 100644
--- a/mozilla/toolkit/components/url-classifier/src/nsUrlClassifierDBService.cpp
+++ b/mozilla/toolkit/components/url-classifier/src/nsUrlClassifierDBService.cpp
@@ -3376,7 +3376,7 @@ nsUrlClassifierDBService::ResetDatabase()
   return mWorkerProxy->ResetDatabase();
 }
 
-NS_IMETHODIMP
+nsresult
 nsUrlClassifierDBService::CacheCompletions(nsTArray<nsUrlClassifierLookupResult> *results)
 {
   NS_ENSURE_TRUE(gDbBackgroundThread, NS_ERROR_NOT_INITIALIZED);