diff --git a/sdmetrics/utils.py b/sdmetrics/utils.py
index e1c1bfca..5c937459 100644
--- a/sdmetrics/utils.py
+++ b/sdmetrics/utils.py
@@ -196,7 +196,7 @@ def transform(self, data):
                 integers = pd.to_numeric(
                     data[field], errors='coerce').to_numpy().astype(np.float64)
                 integers[nulls] = np.nan
-                data[field] = pd.Series(integers)
+                data[field] = pd.Series(integers, index=data.index)
                 data[field] = data[field].fillna(transform_info['mean'])
 
         return data