diff --git a/tensor2tensor/models/transformer.py b/tensor2tensor/models/transformer.py
index 1220aa197..c4c2df86b 100644
--- a/tensor2tensor/models/transformer.py
+++ b/tensor2tensor/models/transformer.py
@@ -225,6 +225,13 @@ def _beam_decode(self, features, decode_length, beam_size, top_beams, alpha):
               None if using greedy decoding (beam_size=1)
       }
     """
+    if self._hparams.self_attention_type != "dot_product":
+      # Caching is not guaranteed to work with attention types other than
+      # dot_product.
+      # TODO(petershaw): Support fast decoding when using relative
+      # position representations, i.e. "dot_product_relative" attention.
+      return self._beam_decode_slow(features, decode_length, beam_size,
+                                    top_beams, alpha)
     with tf.variable_scope(self.name):
       return self._fast_decode(
           features, decode_length, beam_size, top_beams, alpha)