diff --git a/man3/fopen.3 b/man3/fopen.3
index aa7cf97ae..ad04e4231 100644
--- a/man3/fopen.3
+++ b/man3/fopen.3
@@ -284,6 +284,7 @@ is only attempted for a file opened for reading.
 .TP
 .B x
 .\" Since glibc 2.0?
+.\" FIXME C11 specifies this flag
 Open the file exclusively
 (like the
 .B O_EXCL