diff --git a/doc/grep.in.1 b/doc/grep.in.1
index 3e6a8cf..480f205 100644
--- a/doc/grep.in.1
+++ b/doc/grep.in.1
@@ -97,13 +97,15 @@ as an extended regular expression (ERE, see below).
 .RB ( \-E
 is specified by \s-1POSIX\s0.)
 .TP
-.BR \-F ", " \-\^\-fixed\-strings
+.BR \-F ", " \-\^\-fixed\-strings ", " \-\^\-fixed\-regexp
 Interpret
 .I PATTERN
 as a list of fixed strings, separated by newlines,
 any of which is to be matched.
 .RB ( \-F
-is specified by \s-1POSIX\s0.)
+is specified by \s-1POSIX\s0,
+.BR \-\^\-fixed\-regexp
+is an obsoleted alias, please do not use it in new scripts.)
 .TP
 .BR \-G ", " \-\^\-basic\-regexp
 Interpret