diff --git a/shopping_client/shopping_client.py b/shopping_client/shopping_client.py
index 3e53f38c1597f301bb0fbd8fd4b48dd2edc11fb7..d27013e356719542ca5e29b41a25f1d38bc520b9 100644
--- a/shopping_client/shopping_client.py
+++ b/shopping_client/shopping_client.py
@@ -90,7 +90,7 @@ class shopping_client:
 
         return self.basket
 
-    def _is_valid_token(token: Optional[str]) -> bool:
+    def _is_valid_token(self, token: Optional[str]) -> bool:
         """ Checks expiry of the token """
 
         if token is None: