diff --git a/src/snowflake/snowpark/dataframe_reader.py b/src/snowflake/snowpark/dataframe_reader.py
index 81bdb62e1f7..08fa27582fd 100644
--- a/src/snowflake/snowpark/dataframe_reader.py
+++ b/src/snowflake/snowpark/dataframe_reader.py
@@ -322,7 +322,7 @@ def _get_metadata_project_and_schema(self) -> Tuple[List[str], List[Attribute]]:
 
         metadata_schema = []
 
-        def _get_unaliased_name(unaliased: ColumnOrName):
+        def _get_unaliased_name(unaliased: ColumnOrName) -> str:
             if isinstance(unaliased, Column):
                 if isinstance(unaliased._expression, Alias):
                     return unaliased._expression.child.sql