diff --git a/src/boards/bmc830425C4391t.c b/src/boards/bmc830425C4391t.c
index 108425a..475c097 100644
--- a/src/boards/bmc830425C4391t.c
+++ b/src/boards/bmc830425C4391t.c
@@ -42,6 +42,7 @@ static void Sync(void) {
 	setprg16(0x8000, (outer_bank << 3) | (inner_bank & bank_size));
 	setprg16(0xC000, (outer_bank << 3) | bank_size);
 	setchr8(0);
+	setmirror(outer_bank &0x08? MI_H: MI_V);
 }
 
 static DECLFW(M320Write) {