diff --git a/tensorflow/python/ops/array_ops.py b/tensorflow/python/ops/array_ops.py
index 232a77c8888..6fdc50733a1 100644
--- a/tensorflow/python/ops/array_ops.py
+++ b/tensorflow/python/ops/array_ops.py
@@ -120,7 +120,7 @@ def expand_dims(input, axis=None, name=None, dim=None):
     axis: 0-D (scalar). Specifies the dimension index at which to
       expand the shape of `input`. Must be in the range
       `[-rank(input) - 1, rank(input)]`.
-    name: The name of the output `Tensor`.
+    name: The name of the output `Tensor` (optional).
     dim: 0-D (scalar). Equivalent to `axis`, to be deprecated.
 
   Returns:
@@ -128,9 +128,11 @@ def expand_dims(input, axis=None, name=None, dim=None):
     dimension of size 1 added.
 
   Raises:
-    ValueError: if both `dim` and `axis` are specified.
+    ValueError: if either both or neither of `dim` and `axis` are specified.
   """
   axis = deprecation.deprecated_argument_lookup("axis", axis, "dim", dim)
+  if axis is None:
+    raise ValueError("Must specify an axis argument to tf.expand_dims()")
   return gen_array_ops.expand_dims(input, axis, name)