diff --git a/keras.py b/keras.py
index c211feb25cb1ef26fe27280de5bd30e089d3cce4..a87629ad7e34d049d61d211135455538bcce3d4e 100644
--- a/keras.py
+++ b/keras.py
@@ -130,10 +130,17 @@ class KFeed(object):
         return self.gensteps(*args, **kwargs)[0]
 
 
-def Normal(ref, **kwargs):
-    """ Normalizing layer according to ref """
+def Normal(ref, indices=None, **kwargs):
+    """
+    Normalizing layer according to ref.
+    If given, only the variables corresponding to indices will be normalized.
+    """
     mean = ref.mean(**kwargs)
     std = ref.std(**kwargs)
+    if indices:
+        replace = np.isin(np.arange(len(mean)), indices, invert=True)
+        mean[replace] = 0
+        std[replace] = 1
     mul = 1.0 / std
     add = -mean / std
     return tf.keras.layers.Lambda(lambda x: (x * mul) + add)