diff --git a/winsup/cygwin/release/1.7.17 b/winsup/cygwin/release/1.7.17
index 9d295cb6a..c8442ee5d 100644
--- a/winsup/cygwin/release/1.7.17
+++ b/winsup/cygwin/release/1.7.17
@@ -4,6 +4,9 @@ What's new:
 - Support the "e" flag to fopen(3).  This is a Glibc extension which
   allows to fopen the file with the O_CLOEXEC flag set.
 
+- Support the "x" flag to fopen(3).  This is a Glibc/C11 extension which
+  allows to open the file with the O_EXCL flag set.
+
 
 Bug fixes:
 ----------