diff --git a/pymc_marketing/mmm/validating.py b/pymc_marketing/mmm/validating.py
index 16983b6e..f4688b08 100644
--- a/pymc_marketing/mmm/validating.py
+++ b/pymc_marketing/mmm/validating.py
@@ -12,14 +12,6 @@
 ]
 
 
-def _has_valid_indices(df: pd.DataFrame) -> bool:
-    return (
-        isinstance(df.index, pd.RangeIndex)
-        and df.index.start == 0
-        and df.index.stop == len(df)
-    )
-
-
 def validation_method_y(method: Callable) -> Callable:
     if not hasattr(method, "_tags"):
         method._tags = {}  # type: ignore
@@ -49,7 +41,11 @@ def validate_date_col(self, data: pd.DataFrame) -> None:
         if self.date_column not in data.columns:
             raise ValueError(f"date_col {self.date_column} not in data")
 
-        if not _has_valid_indices(data):
+        if (
+            not isinstance(data.index, pd.RangeIndex)
+            or data.index.start != 0
+            or data.index.stop != len(data)
+        ):
             raise ValueError(
                 "X or y has incorrect indices. Try to reset with `data.reset_index(inplace=True)`"
             )