diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 32ca9af3d..fa3700440 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,7 @@
+2011-03-03  Corinna Vinschen  <corinna@vinschen.de>
+
+	* errno.cc (__xpg_strerror_r): Add accidentally missing condition.
+
 2011-03-02  Corinna Vinschen  <corinna@vinschen.de>
 
 	* fhandler_procsys.cc (fhandler_procsys::open): Call worker exists
diff --git a/winsup/cygwin/errno.cc b/winsup/cygwin/errno.cc
index 8ee2a7563..eb9fa3dfd 100644
--- a/winsup/cygwin/errno.cc
+++ b/winsup/cygwin/errno.cc
@@ -395,6 +395,7 @@ __xpg_strerror_r (int errnum, char *buf, size_t n)
     return ERANGE;
   int result = 0;
   char *error = strerror_worker (errnum);
+  if (!error)
     {
       __small_sprintf (error = _my_tls.locals.strerror_buf, "Unknown error %u",
 		       (unsigned) errnum);