diff --git a/tools/libs/guest/xg_dom_arm.c b/tools/libs/guest/xg_dom_arm.c
index b4c24f15fb..01e85e0ea9 100644
--- a/tools/libs/guest/xg_dom_arm.c
+++ b/tools/libs/guest/xg_dom_arm.c
@@ -195,7 +195,7 @@ static int vcpu_arm64(struct xc_dom_image *dom)
 
 /* ------------------------------------------------------------------------ */
 
-static int set_mode(xc_interface *xch, uint32_t domid, char *guest_type)
+static int set_mode(xc_interface *xch, uint32_t domid, const char *guest_type)
 {
     static const struct {
         char           *guest;