--- src/on.xpm.orig	2018-02-10 09:57:51 UTC
+++ src/on.xpm
@@ -1,5 +1,5 @@
 /* XPM */
-static char * on_xpm[] = {
+static const char * on_xpm[] = {
 "12 32 3 1",
 " 	c None",
 ".	c #FFFF00",