diff --git a/desmume/src/MMU.cpp b/desmume/src/MMU.cpp
index bff446247..f86bcc7f4 100644
--- a/desmume/src/MMU.cpp
+++ b/desmume/src/MMU.cpp
@@ -236,7 +236,7 @@ u32 MMU_struct::MMU_MASK[2][256] = {
 		/* 2X*/	DUP16(0x003FFFFF),
 		/* 3X*/	DUP8(0x00007FFF),
 				DUP8(0x0000FFFF),
-		/* 4X*/	DUP8(0x00FFFFFF),
+		/* 4X*/	DUP8(0x0000FFFF),
 				DUP8(0x0000FFFF),
 		/* 5X*/	DUP16(0x00000003),
 		/* 6X*/	DUP16(0x00FFFFFF),