diff --git a/biapy/data/generators/test_pair_data_generators.py b/biapy/data/generators/test_pair_data_generators.py
index cb1cc18f..182c8811 100644
--- a/biapy/data/generators/test_pair_data_generators.py
+++ b/biapy/data/generators/test_pair_data_generators.py
@@ -142,7 +142,8 @@ def __init__(self, ndim, X=None, d_path=None, test_by_chunks=False, provide_Y=Fa
                             self.data[f"sample_{c}"]["gt"] = os.path.join(dm_path,self.data_mask_path[i],gt_image_path)
                         c += 1
 
-                self.len = len(self.data)
+                self.sample_list = list(self.data.keys())
+                self.len = len(self.sample_list)
                 if self.len == 0:
                     raise ValueError("No image found in {}".format(d_path))
             else:
@@ -159,7 +160,6 @@ def __init__(self, ndim, X=None, d_path=None, test_by_chunks=False, provide_Y=Fa
                         raise ValueError("No test image found in {}".format(d_path))
         else:
             self.len = len(X)
-        self.o_indexes = np.arange(self.len)
         
         # Check if a division is required
         self.X_norm = {}
@@ -278,11 +278,12 @@ def load_sample(self, idx):
         # Choose the data source
         if self.X is None:
             if not self.all_files_in_same_folder:
-                img = imread(self.data[f"sample_{idx}"]["raw"])
+                k = self.sample_list[idx]
+                img = imread(self.data[k]["raw"])
                 img = np.squeeze(img)
-                filename = self.data[f"sample_{idx}"]["raw"]
+                filename = self.data[k]["raw"]
                 if self.provide_Y:
-                    mask = imread(self.data[f"sample_{idx}"]["gt"])
+                    mask = imread(self.data[k]["gt"])
                     mask = np.squeeze(mask)   
             else:
                 filename = os.path.join(self.d_path, self.data_path[idx])