diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index c70804e..aeafdda 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -665,6 +665,14 @@
 
         w = Target()
 
+    def test_init(self):
+        # Issue 3634
+        # <weakref to class>.__init__() doesn't check errors correctly
+        r = weakref.ref(Exception)
+        self.assertRaises(TypeError, r.__init__, 0, 0, 0, 0, 0)
+        # No exception should be raised here
+        gc.collect()
+
 
 class SubclassableWeakrefTestCase(TestBase):
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 1fca795..4a201f2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #3634: _weakref.ref(Exception).__init__() gave invalid return value on
+  error.
+
 - Issue #3777: long() applied to a float object now always return a long
   object; previously an int would be returned for small values. the __long__
   method is allowed to return either an int or a long, but the behaviour of
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 5cd9173..9cdd021 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -326,7 +326,7 @@
     if (parse_weakref_init_args("__init__", args, kwargs, &tmp, &tmp))
         return 0;
     else
-        return 1;
+        return -1;
 }