diff -r 99263132665b tools/xenstore/xenstored_domain.c
--- a/tools/xenstore/xenstored_domain.c	Fri May 18 12:38:55 2012 +0200
+++ b/tools/xenstore/xenstored_domain.c	Tue May 22 17:25:03 2012 +0200
@@ -167,7 +167,7 @@ static int readchn(struct connection *co
 
 static void *map_interface(domid_t domid, unsigned long mfn)
 {
-	if (*xcg_handle >= 0) {
+	if (*xcg_handle != NULL) {
 		/* this is the preferred method */
 		return xc_gnttab_map_grant_ref(*xcg_handle, domid,
 			GNTTAB_RESERVED_XENSTORE, PROT_READ|PROT_WRITE);
@@ -179,7 +179,7 @@ static void *map_interface(domid_t domid
 
 static void unmap_interface(void *interface)
 {
-	if (*xcg_handle >= 0)
+	if (*xcg_handle != NULL)
 		xc_gnttab_munmap(*xcg_handle, interface, 1);
 	else
 		munmap(interface, getpagesize());