diff --git a/src/include/86box/vid_svga.h b/src/include/86box/vid_svga.h
index e843bbb95..73c176742 100644
--- a/src/include/86box/vid_svga.h
+++ b/src/include/86box/vid_svga.h
@@ -23,6 +23,7 @@
 #define FLAG_EXT_WRITE		4
 #define FLAG_LATCH8		8
 #define FLAG_NOSKEW		16
+#define FLAG_ADDR_BY16	32
 
 
 typedef struct {
diff --git a/src/video/vid_cl54xx.c b/src/video/vid_cl54xx.c
index 5725d8914..777fdb348 100644
--- a/src/video/vid_cl54xx.c
+++ b/src/video/vid_cl54xx.c
@@ -901,6 +901,8 @@ gd54xx_out(uint16_t addr, uint8_t val, void *p)
 						svga->adv_flags |= FLAG_EXT_WRITE;
 					if (svga->gdcreg[0xb] & 0x08)
 						svga->adv_flags |= FLAG_LATCH8;
+					if (svga->gdcreg[0xb] & 0x10)
+						svga->adv_flags |= FLAG_ADDR_BY16;
 					gd54xx_recalc_banking(gd54xx);
 					break;
 
@@ -1994,7 +1996,7 @@ gd54xx_write_modes45(svga_t *svga, uint8_t val, uint32_t addr)
 
     switch (svga->writemode) {
 	case 4:
-		if (svga->gdcreg[0xb] & 0x10) {
+		if (svga->adv_flags & FLAG_ADDR_BY16) {
 			addr <<= 2;
 			addr &= svga->decode_mask;
 
@@ -2016,7 +2018,7 @@ gd54xx_write_modes45(svga_t *svga, uint8_t val, uint32_t addr)
 		break;
 
 	case 5:
-		if (svga->gdcreg[0xb] & 0x10) {
+		if (svga->adv_flags & FLAG_ADDR_BY16) {
 			addr <<= 2;
 			addr &= svga->decode_mask;
 
diff --git a/src/video/vid_svga.c b/src/video/vid_svga.c
index 2dbd1566f..07f6f3823 100644
--- a/src/video/vid_svga.c
+++ b/src/video/vid_svga.c
@@ -1056,9 +1056,11 @@ svga_write_common(uint32_t addr, uint8_t val, uint8_t linear, void *p)
     }
 
     if (!(svga->gdcreg[6] & 1))
-	svga->fullchange = 2;
+		svga->fullchange = 2;
 
-    if ((svga->adv_flags & FLAG_ADDR_BY8) && (svga->writemode < 4))
+	if ((svga->adv_flags & FLAG_ADDR_BY16) && (svga->writemode == 4 || svga->writemode == 5))
+	addr <<= 4;
+    else if ((svga->adv_flags & FLAG_ADDR_BY8) && (svga->writemode < 4))
 	addr <<= 3;
     else if (((svga->chain4 && svga->packed_chain4) || svga->fb_only) && (svga->writemode < 4)) {
 	writemask2 = 1 << (addr & 3);
@@ -1244,7 +1246,9 @@ svga_read_common(uint32_t addr, uint8_t linear, void *p)
     latch_addr = (addr << count) & svga->decode_mask;
     count = (1 << count);
 
-    if (svga->adv_flags & FLAG_ADDR_BY8)
+	if (svga->adv_flags & FLAG_ADDR_BY16)
+	addr <<= 4;
+    else if (svga->adv_flags & FLAG_ADDR_BY8)
 	addr <<= 3;
     else if ((svga->chain4 && svga->packed_chain4) || svga->fb_only) {
 	addr &= svga->decode_mask;