diff --git a/src/wormhole/test/test_wormhole.py b/src/wormhole/test/test_wormhole.py
index eae68af..68d5679 100644
--- a/src/wormhole/test/test_wormhole.py
+++ b/src/wormhole/test/test_wormhole.py
@@ -826,9 +826,12 @@ class Wormholes(ServerBase, unittest.TestCase):
         code = yield w1.get_code()
         code_no_dashes = code.replace('-', ' ')
 
-        with self.assertRaises(KeyFormatError):
+        with self.assertRaises(KeyFormatError) as ex:
             w2.set_code(code_no_dashes)
 
+        expected_msg = "code (%s) contains spaces." % (code_no_dashes,)
+        self.assertEqual(expected_msg, str(ex.exception))
+
         yield w1.close()
         yield w2.close()
         self.flushLoggedErrors(ValueError)
diff --git a/src/wormhole/wormhole.py b/src/wormhole/wormhole.py
index 1607413..7392433 100644
--- a/src/wormhole/wormhole.py
+++ b/src/wormhole/wormhole.py
@@ -479,10 +479,7 @@ class _Wormhole:
         # bail out early if the password contains spaces...
         # this should raise a useful error
         if ' ' in code:
-            raise KeyFormatError(
-                "code (%s) contains spaces. Words must be separated by dashes"
-                % code
-            )
+            raise KeyFormatError("code (%s) contains spaces." % code)
         self._code = code
         mo = re.search(r'^(\d+)-', code)
         if not mo: