diff --git a/docs/changes.rst b/docs/changes.rst
index 03d7ba1b..3de2c81e 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -11,6 +11,13 @@ Version 1.12.0
   to access the true type of the base class using ``__wrapped__`` in
   the inherited class list of the derived class.
 
+**Bugs Fixed**
+
+* When using the ``synchronized`` decorator on instance methods of a
+  class, if the class declared special methods to override the result for
+  when the class instance was tested as a boolean so that it returned
+  ``False`` all the time, the synchronized method would fail when called.
+
 Version 1.11.2
 --------------
 
diff --git a/tests/test_synchronized_lock.py b/tests/test_synchronized_lock.py
index af654d43..6e7eb12d 100644
--- a/tests/test_synchronized_lock.py
+++ b/tests/test_synchronized_lock.py
@@ -55,6 +55,18 @@ def function3():
 
 c4 = C4()
 
+class C5(object):
+
+    def __bool__(self):
+        return False
+    __nonzero__=__bool__
+
+    @wrapt.synchronized
+    def function1(self):
+        print('function1')
+
+c5 = C5()
+
 class TestSynchronized(unittest.TestCase):
 
     def test_synchronized_function(self):
@@ -261,5 +273,16 @@ def test_synchronized_type_old_style(self):
         self.assertNotEqual(_lock3, None)
         self.assertEqual(_lock3, _lock2)
 
+    def test_synchronized_false_instance(self):
+        c5.function1()
+
+        self.assertEqual(bool(c5), False)
+
+        _lock1 = getattr(C5, '_synchronized_lock', None)
+        self.assertEqual(_lock1, None)
+
+        _lock2 = getattr(c5, '_synchronized_lock', None)
+        self.assertNotEqual(_lock2, None)
+
 if __name__ == '__main__':
     unittest.main()