diff --git a/src/pudl/analysis/record_linkage/classify_plants_ferc1.py b/src/pudl/analysis/record_linkage/classify_plants_ferc1.py
index ce9688f790..9cb41e4368 100644
--- a/src/pudl/analysis/record_linkage/classify_plants_ferc1.py
+++ b/src/pudl/analysis/record_linkage/classify_plants_ferc1.py
@@ -37,7 +37,7 @@ def __init__(self, plants_steam_df, metric="euclidean", penalty=100):
             metric: Distance metric to use in computation.
             penalty: Penalty to apply to records with the same report year.
         """
-        self.df = plants_steam_df
+        self.plants_steam_df = plants_steam_df
         self.metric = metric
         self.penalty = penalty
 
@@ -48,11 +48,14 @@ def fit(self, X, y=None, **fit_params):  # noqa: N803
     def transform(self, X, y=None, **fit_params):  # noqa: N803
         """Compute distance between records then add penalty to records from same year."""
         dist_matrix = pairwise_distances(X, metric=self.metric)
-        report_years = range(self.df.report_year.min(), self.df.report_year.max() + 1)
+        report_years = range(
+            self.plants_steam_df.report_year.min(),
+            self.plants_steam_df.report_year.max() + 1,
+        )
         penalty_matrix = np.full(dist_matrix.shape, 0)
         for yr in report_years:
             # get the indices of all the record pairs that have matching report years
-            yr_idx = self.df[self.df.report_year == yr].index
+            yr_idx = self.plants_steam_df[self.plants_steam_df.report_year == yr].index
             yr_match_pairs_idx = np.array(np.meshgrid(yr_idx, yr_idx)).T.reshape(-1, 2)
             idx_x = yr_match_pairs_idx[:, 0]
             idx_y = yr_match_pairs_idx[:, 1]