diff --git a/hamilton/function_modifiers/validation.py b/hamilton/function_modifiers/validation.py
index 2af8f0a8a..5a6dd055b 100644
--- a/hamilton/function_modifiers/validation.py
+++ b/hamilton/function_modifiers/validation.py
@@ -168,7 +168,7 @@ def some_int_data_between_0_and_100() -> pd.Series:
         schema = pa.DataFrameSchema(...)
 
         @extract_columns('col1', 'col2')
-        @check_output(schema=schema, target_="builds_dataframe, importance="fail")
+        @check_output(schema=schema, target_="builds_dataframe", importance="fail")
         def builds_dataframe(...) -> pd.DataFrame:
             ...