# HG changeset patch
# Parent 9354df85afd70c3211f8c0037f8087905b55d89d

diff --git a/Lib/threading.py b/Lib/threading.py
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -287,10 +287,12 @@
     def __init__(self, value=1):
         Semaphore.__init__(self, value)
         self._initial_value = value
+        self.TESTWAIT = Event()
 
     def release(self):
         if self._value >= self._initial_value:
             raise ValueError("Semaphore released too many times")
+        self.TESTWAIT.wait()
         return Semaphore.release(self)
 
 
diff --git a/unbounded.py b/unbounded.py
new file mode 100644
--- /dev/null
+++ b/unbounded.py
@@ -0,0 +1,20 @@
+from threading import BoundedSemaphore, Thread
+
+bs = BoundedSemaphore(1)
+
+def runner1():
+    bs.acquire()
+    bs.release()
+
+def runner2():
+    bs.release()
+
+threads = [Thread(target=runner1), Thread(target=runner2)]
+for t in threads:
+    t.start()
+
+bs.TESTWAIT.set()
+for t in threads:
+    t.join()
+
+print("bs._value is {}".format(bs._value))