diff --git a/tensorflow/python/ops/rnn.py b/tensorflow/python/ops/rnn.py
index e010e371a71644..ad916b6b5fa7b6 100644
--- a/tensorflow/python/ops/rnn.py
+++ b/tensorflow/python/ops/rnn.py
@@ -269,6 +269,10 @@ def _reverse_seq(input_seq, lengths):
   # Join into (time, batch_size, depth)
   s_joined = array_ops.pack(input_seq)
 
+  # TODO(schuster, ebrevdo): Remove cast when reverse_sequence takes int32
+  if lengths is not None:
+    lengths = math_ops.to_int64(lengths)
+
   # Reverse along dimension 0
   s_reversed = array_ops.reverse_sequence(s_joined, lengths, 0, 1)
   # Split again into list