diff --git a/zsnes/src/video/hq4x16.asm b/zsnes/src/video/hq4x16.asm
index b33ad94c..03d21928 100644
--- a/zsnes/src/video/hq4x16.asm
+++ b/zsnes/src/video/hq4x16.asm
@@ -4182,6 +4182,9 @@ HighResProc:
     ret
 .m56
     mov ebx,[NumBytesPerLine]
+    mov eax,edi
+    add eax,ebx
+    add eax,ebx
     test byte[cfield],1
     jnz .cfield1hr
 .cfield0hr