diff --git a/libc/docs/CHANGES.TXT b/libc/docs/CHANGES.TXT
index e818df3..47289f6 100644
--- a/libc/docs/CHANGES.TXT
+++ b/libc/docs/CHANGES.TXT
@@ -64,6 +64,10 @@
   in /etc/resolv.conf. (resolv.conf is already ignored, so the latter
   is a no-op for actual functionality.)
 
+- fix pthread_sigmask() to properly return an error code without touching
+  errno. Previous implementation returned -1 on error, setting errno, which
+  is not Posix compliant.
+
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 Differences between Android 2.1 and 2.0.1: