diff --git a/mapie/estimator/regressor.py b/mapie/estimator/regressor.py
index b6ee9ba41..121240f24 100644
--- a/mapie/estimator/regressor.py
+++ b/mapie/estimator/regressor.py
@@ -485,8 +485,8 @@ def fit_multi_estimators(
 
         if self.cv == "prefit":
 
-            # self.k_ is defined but not used
-            # Because it is among the fit attributes
+            # Create a placeholder attribute 'k_' filled with NaN values
+            # (This attribute is defined for consistency but is not used in prefit mode)
             self.k_ = np.full(
                 shape=(n_samples, 1), fill_value=np.nan, dtype=float
             )