diff --git a/ui/vnc.c b/ui/vnc.c
index 3ccd33dedc..310a873c21 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -3098,6 +3098,9 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
     VncState *vs;
     int has_dirty = 0;
     pixman_image_t *tmpbuf = NULL;
+    unsigned long offset;
+    int x;
+    uint8_t *guest_ptr, *server_ptr;
 
     struct timeval tv = { 0, 0 };
 
@@ -3106,6 +3109,13 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
         has_dirty = vnc_update_stats(vd, &tv);
     }
 
+    offset = find_next_bit((unsigned long *) &vd->guest.dirty,
+                           height * VNC_DIRTY_BPL(&vd->guest), 0);
+    if (offset == height * VNC_DIRTY_BPL(&vd->guest)) {
+        /* no dirty bits in guest surface */
+        return has_dirty;
+    }
+
     /*
      * Walk through the guest dirty map.
      * Check and copy modified bits from guest to server surface.
@@ -3130,15 +3140,6 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
     line_bytes = MIN(server_stride, guest_ll);
 
     for (;;) {
-        int x;
-        uint8_t *guest_ptr, *server_ptr;
-        unsigned long offset = find_next_bit((unsigned long *) &vd->guest.dirty,
-                                             height * VNC_DIRTY_BPL(&vd->guest),
-                                             y * VNC_DIRTY_BPL(&vd->guest));
-        if (offset == height * VNC_DIRTY_BPL(&vd->guest)) {
-            /* no more dirty bits */
-            break;
-        }
         y = offset / VNC_DIRTY_BPL(&vd->guest);
         x = offset % VNC_DIRTY_BPL(&vd->guest);
 
@@ -3177,6 +3178,13 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
         }
 
         y++;
+        offset = find_next_bit((unsigned long *) &vd->guest.dirty,
+                               height * VNC_DIRTY_BPL(&vd->guest),
+                               y * VNC_DIRTY_BPL(&vd->guest));
+        if (offset == height * VNC_DIRTY_BPL(&vd->guest)) {
+            /* no more dirty bits */
+            break;
+        }
     }
     qemu_pixman_image_unref(tmpbuf);
     return has_dirty;