diff --git a/protovalidate/internal/extra_func.py b/protovalidate/internal/extra_func.py
index 5caaaa50..386020ee 100644
--- a/protovalidate/internal/extra_func.py
+++ b/protovalidate/internal/extra_func.py
@@ -332,7 +332,7 @@ def cel_is_inf(val: celtypes.Value, sign: typing.Optional[celtypes.Value] = None
 
 
 def cel_unique(val: celtypes.Value) -> celpy.Result:
-    if not isinstance(val, celtypes.ListType) and not isinstance(val, list):
+    if not isinstance(val, (celtypes.ListType, list)):
         msg = "invalid argument, expected list"
         raise celpy.CELEvalError(msg)
     return celtypes.BoolType(len(val) == len(set(val)))