diff --git a/Lib/inspect.py b/Lib/inspect.py
index d6bd8cd..020a263 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1528,6 +1528,20 @@ def signature(obj):
                 init = _get_user_defined_method(obj, '__init__')
                 if init is not None:
                     sig = signature(init)
+
+        if sig is None and obj not in (object, type):
+            # We have a class, but no user-defined
+            # __init__ or __new__ for it
+            if type in obj.__mro__:
+                # It's a metaclass. Return signature of 'type.__new__':
+                # (name, bases, dct)
+                return Signature([Parameter('name', _POSITIONAL_ONLY),
+                                  Parameter('bases', _POSITIONAL_ONLY),
+                                  Parameter('dct', _POSITIONAL_ONLY)])
+            else:
+                # It's a class, return empty signature
+                return Signature()
+
     elif not isinstance(obj, _NonUserDefinedCallables):
         # An object with __call__
         # We also check that the 'obj' is not an instance of
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 1bfe724..81791f3 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -1964,6 +1964,22 @@ class TestSignatureObject(unittest.TestCase):
                            ('bar', 2, ..., "keyword_only")),
                           ...))
 
+        # Test classes without user-defined __init__ or __new__
+        class C: pass
+        self.assertEqual(self.signature(C), ((), ...))
+        class D(C): pass
+        self.assertEqual(self.signature(D), self.signature(C))
+
+        # Test meta classes without user-defined __init__ or __new__
+        class CM(type): pass
+        class DM(CM): pass
+        self.assertEqual(self.signature(CM),
+                         ((('name', ..., ..., 'positional_only'),
+                           ('bases', ..., ..., 'positional_only'),
+                           ('dct', ..., ..., 'positional_only')),
+                          ...))
+        self.assertEqual(self.signature(CM), self.signature(DM))
+
     def test_signature_on_callable_objects(self):
         class Foo:
             def __call__(self, a):