--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -1101,20 +1101,22 @@ private:
 
   static void HandleError(const char* aMsg)
   {
     nsresult rv;
     nsCOMPtr<nsIConsoleService> console =
       do_GetService("@mozilla.org/consoleservice;1", &rv);
     if (NS_SUCCEEDED(rv)) {
       console->LogStringMessage(NS_ConvertUTF8toUTF16(aMsg).get());
-    } else {
-      printf_stderr("%s\n", aMsg);
     }
-    NS_WARNING(aMsg);
+#ifdef DEBUG
+    NS_ERROR(aMsg);
+#else
+    printf_stderr("%s\n", aMsg);
+#endif
   }
 
   // This is static so that HandlePref() can increment it easily. This is ok
   // because prefs files are read one at a time.
   static uint32_t sNumPrefs;
 };
 
 uint32_t Parser::sNumPrefs = 0;