diff --git a/pandas/core/index.py b/pandas/core/index.py
index 8b650fea9b440..83f60b360c746 100644
--- a/pandas/core/index.py
+++ b/pandas/core/index.py
@@ -1357,7 +1357,7 @@ def difference(self, other):
         theDiff = sorted(set(self) - set(other))
         return Index(theDiff, name=result_name)
 
-    diff = deprecate('diff',difference)
+    diff = deprecate('diff', difference)
 
     def sym_diff(self, other, result_name=None):
         """
diff --git a/pandas/tests/test_index.py b/pandas/tests/test_index.py
index 4156199f34851..313a723f7b1ef 100644
--- a/pandas/tests/test_index.py
+++ b/pandas/tests/test_index.py
@@ -769,7 +769,7 @@ def test_difference(self):
         self.assertEqual(result.name, first.name)
 
         # non-iterable input
-        assertRaisesRegexp(TypeError, "iterable", first.diff, 0.5)
+        assertRaisesRegexp(TypeError, "iterable", first.difference, 0.5)
 
     def test_symmetric_diff(self):
         # smoke