diff --git a/superset/common/query_context_factory.py b/superset/common/query_context_factory.py
index 3a8380bdb0c82..a42d1d4ba7316 100644
--- a/superset/common/query_context_factory.py
+++ b/superset/common/query_context_factory.py
@@ -121,7 +121,7 @@ def _apply_granularity(
         datasource: BaseDatasource,
     ) -> None:
         temporal_columns = {
-            column.column_name
+            column["column_name"] if isinstance(column, dict) else column.column_name
             for column in datasource.columns
             if (column["is_dttm"] if isinstance(column, dict) else column.is_dttm)
         }