diff --git a/tiramisu/value.py b/tiramisu/value.py
index d7f0c0b..27f6302 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -235,6 +235,8 @@ class Values:
                        value: Any,
                        force_allow_empty_list: bool,
                        ) -> bool:
+        if not isinstance(value, list):
+            return False
         return (not force_allow_empty_list and value == []) or None in value or '' in value
 
     #______________________________________________________________________