diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index ce25d8d..cc9da05 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -277,6 +277,12 @@
         import os
         if not hasattr(os, 'fork'):
             return
+        # Skip platforms with known problems forking from a worker thread.
+        # See http://bugs.python.org/issue3863.
+        if sys.platform in ('freebsd4', 'freebsd5', 'freebsd6', 'os2emx'):
+            print >>sys.stderr, ('Skipping test_3_join_in_forked_from_thread'
+                                 ' due to known OS bugs on'), sys.platform
+            return
         script = """if 1:
             main_thread = threading.currentThread()
             def worker():
diff --git a/Misc/NEWS b/Misc/NEWS
index a98ae2c..435961c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -250,6 +250,9 @@
 Tests
 -----
 
+- Issue #3863: Disabled a unit test of fork being called from a thread
+  when running on platforms known to exhibit OS bugs when attempting that.
+
 - Issue #3261: test_cookielib had an improper file encoding specified.
 
 - Patch #2232: os.tmpfile might fail on Windows if the user has no