diff --git a/hw/display/sm501.c b/hw/display/sm501.c
index b095134d6f..d4878f01c0 100644
--- a/hw/display/sm501.c
+++ b/hw/display/sm501.c
@@ -709,8 +709,8 @@ static void sm501_2d_operation(SM501State *s)
     /* get frame buffer info */
     uint8_t *src = s->local_mem + (s->twoD_source_base & 0x03FFFFFF);
     uint8_t *dst = s->local_mem + (s->twoD_destination_base & 0x03FFFFFF);
-    int src_width = (s->dc_crt_h_total & 0x00000FFF) + 1;
-    int dst_width = (s->dc_crt_h_total & 0x00000FFF) + 1;
+    int src_width = s->twoD_pitch & 0x1FFF;
+    int dst_width = (s->twoD_pitch >> 16) & 0x1FFF;
 
     if (addressing != 0x0) {
         printf("%s: only XY addressing is supported.\n", __func__);