diff --git a/Foundation/CPLocale.j b/Foundation/CPLocale.j
index 01945215c..2d46d68f8 100644
--- a/Foundation/CPLocale.j
+++ b/Foundation/CPLocale.j
@@ -101,7 +101,7 @@ var sharedSystemLocale = nil,
 
             language = [CPString stringWithFormat:@"%s_%s", [language lowercaseString], [language uppercaseString]];
 
-            if ([availableLocaleIdentifiers indexOfObject:language])
+            if ([availableLocaleIdentifiers indexOfObject:language] !== CPNotFound)
                 localeIdentifier = language;
         }