diff --git a/image_ref/dataset_ref.py b/image_ref/dataset_ref.py
index 0fcfbdf70e9768b1f4a0a31ef588ef5396ae17e3..676ed89b9e3d36b6e3839052aa6e4409c9bee076 100644
--- a/image_ref/dataset_ref.py
+++ b/image_ref/dataset_ref.py
@@ -133,7 +133,9 @@ class ImageFolderDuo(data.Dataset):
             if i < self.positive_prop:
                 label_ref = target
             else :
-                label_ref = np.random.randint(0,len(self.classes)-1) #can be postive too (border effect)
+                l = np.arange(0,len(self.classes)-1,dtype=int).tolist()
+                l.remove(target)
+                label_ref = np.random.choice(l)
         else :
             label_ref = np.random.randint(0,len(self.classes)-1)
         class_ref = self.classes[label_ref]