diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index 379910db2dc64f548448b27eddf90015c575c66a..629a5c8b4c640255f99392481edc067dbf2e150b 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -277,10 +277,9 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
     }
     if (pitch < 0) {
         int64_t min = addr
-            + ((int64_t)s->cirrus_blt_height-1) * pitch;
-        int32_t max = addr
-            + s->cirrus_blt_width;
-        if (min < 0 || max > s->vga.vram_size) {
+            + ((int64_t)s->cirrus_blt_height - 1) * pitch
+            - s->cirrus_blt_width;
+        if (min < -1 || addr >= s->vga.vram_size) {
             return true;
         }
     } else {