diff --git a/ChangeLog b/ChangeLog
index 2d596e4f2..fd5801940 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-05-24 Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/NSThread.m: Use lock to prevent race condition setting up
+	runloop info for thread.
+
 2009-05-23 Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/NSKeyValueObserving.m:
diff --git a/Source/NSThread.m b/Source/NSThread.m
index 5f9a15c3c..a9db1a75c 100644
--- a/Source/NSThread.m
+++ b/Source/NSThread.m
@@ -1057,7 +1057,12 @@ GSRunLoopInfoForThread(NSThread *aThread)
     }
   if (((NSThread_ivars*)aThread)->_runLoopInfo == nil)
     {
-      ((NSThread_ivars*)aThread)->_runLoopInfo = [GSRunLoopThreadInfo new];
+      [gnustep_global_lock lock];
+      if (((NSThread_ivars*)aThread)->_runLoopInfo == nil)
+        {
+          ((NSThread_ivars*)aThread)->_runLoopInfo = [GSRunLoopThreadInfo new];
+	}
+      [gnustep_global_lock unlock];
     }
   info = ((NSThread_ivars*)aThread)->_runLoopInfo;
   return info;