diff --git a/src/mame/drivers/pc9801.cpp b/src/mame/drivers/pc9801.cpp
index 1e4cbaf3959..16c34dc56ba 100644
--- a/src/mame/drivers/pc9801.cpp
+++ b/src/mame/drivers/pc9801.cpp
@@ -787,7 +787,7 @@ UPD7220_DISPLAY_PIXELS_MEMBER( pc9801_state::hgdc_display_pixels )
 			res_x = x + xi;
 			res_y = y;
 
-			pen = ext_gvram[((address*16+xi)+(m_vram_disp*0x40000)) >> 1];
+			pen = ext_gvram[(address >> 1)*16+xi+(m_vram_disp*0x20000)];
 
 			bitmap.pix32(res_y, res_x) = palette[pen + 0x20];
 		}