diff --git a/xmenu.1 b/xmenu.1
index 3546f92..f6426a4 100644
--- a/xmenu.1
+++ b/xmenu.1
@@ -6,6 +6,8 @@ xmenu \- menu utility for X
 .RB [ \-irw ]
 .RB [ -p
 .IR position ]
+.RB [ -x|-X
+.RI [ modifier- ] button ]
 .RI [ title ]
 .SH DESCRIPTION
 .B xmenu
diff --git a/xmenu.c b/xmenu.c
index 08b807d..177cf9c 100644
--- a/xmenu.c
+++ b/xmenu.c
@@ -174,7 +174,8 @@ static int niconpaths = 0;              /* number of paths to icon directories *
 static void
 usage(void)
 {
-	(void)fprintf(stderr, "usage: xmenu [-irw] [-p position] [title]\n");
+
+	(void)fprintf(stderr, "usage: xmenu [-irw] [-p position] [(-x|-X) [modifier-]button] [title]\n");
 	exit(1);
 }