diff --git a/WHATSNEW b/WHATSNEW
index 2358d929e81843205c921a4e2d424e3c928a926a..55817aa962b02b1c48cdffb186cba56d02223c16 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -88,7 +88,8 @@ implemented POSIX timers.
 
 optimized and simplified many thread-related functions.
 
-eliminated resource leak races in thread cancellation.
+eliminated resource leak races in thread cancellation. (almost all
+existing implementations, including glibc, have these leaks.)
 
 overhauled stdio implementation to take advantage of readv/writev for
 reduced syscall load, and improved stdio's handling of error status.