diff --git a/setup.py b/setup.py
index 87a55943bbf..f979a291438 100644
--- a/setup.py
+++ b/setup.py
@@ -1258,6 +1258,17 @@ class db_found(Exception): pass
                 HAVE_BROKEN_SEM_UNLINK=1
                 )
             libraries = []
+
+        elif platform in ('freebsd5', 'freebsd6', 'freebsd7', 'freebsd8'):
+            # FreeBSD's P1003.1b semaphore support is very experimental
+            # and has many known problems. (as of June 2008)
+            macros = dict(                  # FreeBSD
+                HAVE_SEM_OPEN=0,
+                HAVE_SEM_TIMEDWAIT=0,
+                HAVE_FD_TRANSFER=1,
+                )
+            libraries = []
+
         else:                                   # Linux and other unices
             macros = dict(
                 HAVE_SEM_OPEN=1,