diff --git a/vnc.c b/vnc.c
index 142e769..a4187a1 100644
--- a/vnc.c
+++ b/vnc.c
@@ -2205,7 +2205,7 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
             guest_ptr  = guest_row;
             server_ptr = server_row;
 
-            for (x = 0; x < vd->guest.ds->width;
+            for (x = 0; x + 15 < vd->guest.ds->width;
                     x += 16, guest_ptr += cmp_bytes, server_ptr += cmp_bytes) {
                 if (!vnc_get_bit(vd->guest.dirty[y], (x / 16)))
                     continue;