diff -r 0909f73cfa3a Lib/unittest/case.py
--- a/Lib/unittest/case.py	Sat Mar 08 16:36:37 2014 +1000
+++ b/Lib/unittest/case.py	Mon Mar 10 22:14:45 2014 -0300
@@ -143,6 +143,14 @@
                 self.obj_name = str(callable_obj)
         else:
             self.obj_name = None
+
+        if expected_regex is None:
+            pass
+        else:
+            if type(expected_regex) is not str:
+                if not isinstance(expected_regex, re._pattern_type):
+                    raise TypeError("Expected regex must be a string or a regex object")
+                    
         if isinstance(expected_regex, (bytes, str)):
             expected_regex = re.compile(expected_regex)
         self.expected_regex = expected_regex
diff -r 0909f73cfa3a Lib/unittest/test/test_case.py
--- a/Lib/unittest/test/test_case.py	Sat Mar 08 16:36:37 2014 +1000
+++ b/Lib/unittest/test/test_case.py	Mon Mar 10 22:14:45 2014 -0300
@@ -1126,6 +1126,25 @@
                 self.assertRaisesRegex, Exception, 'x',
                 lambda: None)
 
+    def testAssertRaisesRegexInvalidRegex(self):
+        class ExceptionMock(Exception):
+            pass
+        
+        def Stub():
+            raise ExceptionMock('We expect')
+
+        self.assertRaises(TypeError, self.assertRaisesRegex, ExceptionMock, 123456, Stub)
+
+
+    def testAssertWarnsRegexInvalidRegex(self):
+        class WarningMock(Warning):
+            pass
+
+        def Stub():
+            raise WarningMock('We expect')
+        
+        self.assertRaises(TypeError, self.assertWarnsRegex, WarningMock, Stub)
+
     def testAssertRaisesRegexMismatch(self):
         def Stub():
             raise Exception('Unexpected')