diff --git a/utilization/dataset/dataset.py b/utilization/dataset/dataset.py
index fcd9eb7c..d876b46c 100644
--- a/utilization/dataset/dataset.py
+++ b/utilization/dataset/dataset.py
@@ -560,7 +560,7 @@ def _format_instance(
             formatted_instance[key] = getattr(self, key)
         for key, value in formatted_instance.items():
             if isinstance(value, str) and value.startswith(" "):
-                warn_once(logger, f"Key `{key}` has leading spaces: {pformat(value)}")(key)
+                warn_once(logger, f"Key `{key}` has leading spaces: {pformat(value)}", key)
 
         if not isinstance(source, list):
             if self.instruction_template.debug_info: