diff --git a/bitly_api/bitly_api.py b/bitly_api/bitly_api.py
index 2a85522..9a8f6c5 100644
--- a/bitly_api/bitly_api.py
+++ b/bitly_api/bitly_api.py
@@ -346,7 +346,7 @@ def user_link_history(self, created_before=None, created_after=None,
         if private is not None:
             assert isinstance(private, string_types)
             private = private.lower()
-            assert private is "on" or "off" or "both"
+            assert private == "on" or "off" or "both"
             params["private"] = private
         if limit is not None:
             assert isinstance(limit, integer_types)