progs/xdemos: fix command line flag typo
diff --git a/progs/xdemos/glsync.c b/progs/xdemos/glsync.c
index 34167d3..da87306 100644
--- a/progs/xdemos/glsync.c
+++ b/progs/xdemos/glsync.c
@@ -95,7 +95,7 @@
 static void usage(char *name)
 {
 	printf("usage: %s [-w <width>] [-h <height>] [-s<sync method>] "
-	       "[-vc]\n", name);
+	       "[-v]\n", name);
 	printf("\t-s<sync method>:\n");
 	printf("\t\tn: none\n");
 	printf("\t\ts: SGI video sync extension\n");