diff --git a/zsnes/src/video/newgfx16.mac b/zsnes/src/video/newgfx16.mac
index 787053c3..c780bb2d 100644
--- a/zsnes/src/video/newgfx16.mac
+++ b/zsnes/src/video/newgfx16.mac
@@ -3300,7 +3300,10 @@ EXTSYM osm2dis
     je near .offsetm16x16
     xor edx,edx
     mov dx,[BG3SYl+ebx*2]
+    test dx,08h
+    jz .overflow
     and dx,0F8h
+.overflow
     shr edx,3
     shl edx,6
     xor eax,eax