Backport of 64903.

Lib/dummy_thread.py

@@ -107,18 +107,15 @@ class LockType(object):
         aren't triggered and throw a little fit.
 
         """
-        if waitflag is None:
+        if waitflag is None or waitflag:
             self.locked_status = True
-            return None
-        elif not waitflag:
+            return True
+        else:
             if not self.locked_status:
                 self.locked_status = True
                 return True
             else:
                 return False
-        else:
-            self.locked_status = True
-            return True
 
     __enter__ = acquire
 

Lib/test/test_dummy_thread.py

@@ -60,6 +60,7 @@ class LockTests(unittest.TestCase):
         #Make sure that an unconditional locking returns True.
         self.failUnless(self.lock.acquire(1) is True,
                         "Unconditional locking did not return True.")
+        self.failUnless(self.lock.acquire() is True)
 
     def test_uncond_acquire_blocking(self):
         #Make sure that unconditional acquiring of a locked lock blocks.