diff --git a/sqlmesh/core/test/definition.py b/sqlmesh/core/test/definition.py
index 1c9807cfa1..8694ec6024 100644
--- a/sqlmesh/core/test/definition.py
+++ b/sqlmesh/core/test/definition.py
@@ -355,11 +355,12 @@ def _to_hashable(x: t.Any) -> t.Any:
                         for df in _split_df_by_column_pairs(diff)
                     )
                 else:
-                    from pandas import MultiIndex
+                    from pandas import DataFrame, MultiIndex
 
                     levels = t.cast(MultiIndex, diff.columns).levels[0]
                     for col in levels:
-                        col_diff = diff[col]
+                        # diff[col] returns a DataFrame when columns is a MultiIndex
+                        col_diff = t.cast(DataFrame, diff[col])
                         if not col_diff.empty:
                             table = df_to_table(
                                 f"[bold red]Column '{col}' mismatch{failed_subtest}[/bold red]",