diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 42d76a3..a005dc4 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -18,6 +18,13 @@
 leverage multiple processors on a given machine.  It runs on both Unix and
 Windows.
 
+.. warning::
+
+    This package largely requires a functioning shared semaphore
+    implementation on the host operating system to function. Without one, the 
+    :mod:`multiprocessing.synchronize` module will be disabled, and attempts to 
+    import it will result in an ImportError. See 
+    http://bugs.python.org/issue3770 for additional information.
 
 The :class:`Process` class
 ~~~~~~~~~~~~~~~~~~~~~~~~~~