diff -r 070fed5b7b9d Lib/inspect.py
--- a/Lib/inspect.py	Thu Sep 11 23:08:48 2014 +0100
+++ b/Lib/inspect.py	Fri Sep 12 10:25:02 2014 -0400
@@ -2542,9 +2542,17 @@
                           return_annotation=return_annotation)
 
     def __hash__(self):
-        hash_tuple = tuple(self.parameters.values())
+        params = tuple(param for param in self.parameters.values()
+                             if param.kind != _KEYWORD_ONLY)
+
+        kwo_params = frozenset(param for param in self.parameters.values()
+                                     if param.kind == _KEYWORD_ONLY)
+
+        hash_tuple = (params, kwo_params)
+
         if self._return_annotation is not _empty:
             hash_tuple += (self._return_annotation,)
+
         return hash(hash_tuple)
 
     def __eq__(self, other):
diff -r 070fed5b7b9d Lib/test/test_inspect.py
--- a/Lib/test/test_inspect.py	Thu Sep 11 23:08:48 2014 +0100
+++ b/Lib/test/test_inspect.py	Fri Sep 12 10:25:02 2014 -0400
@@ -2535,43 +2535,67 @@
 
         def bar(a, *, b:int) -> float: pass
         self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def bar(a, *, b:int) -> int: pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def bar(a, *, b:int): pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def bar(a, *, b:int=42) -> float: pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def bar(a, *, c) -> float: pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def bar(a, b:int) -> float: pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
         def spam(b:int, a) -> float: pass
         self.assertNotEqual(inspect.signature(spam), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(spam)), hash(inspect.signature(bar)))
 
         def foo(*, a, b, c): pass
         def bar(*, c, b, a): pass
         self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def foo(*, a=1, b, c): pass
         def bar(*, c, b, a=1): pass
         self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def foo(pos, *, a=1, b, c): pass
         def bar(pos, *, c, b, a=1): pass
         self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def foo(pos, *, a, b, c): pass
         def bar(pos, *, c, b, a=1): pass
         self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertNotEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
         def foo(pos, *args, a=42, b, c, **kwargs:int): pass
         def bar(pos, *args, c, b, a=42, **kwargs:int): pass
         self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+        self.assertEqual(
+            hash(inspect.signature(foo)), hash(inspect.signature(bar)))
 
     def test_signature_hashable(self):
         S = inspect.Signature