diff --git a/src/gba/io.c b/src/gba/io.c
index d29fb8a4b..8a4ea7fc2 100644
--- a/src/gba/io.c
+++ b/src/gba/io.c
@@ -214,8 +214,8 @@ static const int _isRSpecialRegister[GBA_REG(INTERNAL_MAX)] = {
 	/* 10 */ 1, 1, 1, 1, 1, 1, 1, 1,
 	/* 11 */ 0, 0, 0, 0, 0, 0, 0, 0,
 	/*    SIO */
-	/* 12 */ 1, 1, 1, 1, 1, 0, 0, 0,
-	/* 13 */ 1, 1, 1, 0, 0, 0, 0, 0,
+	/* 12 */ 1, 1, 1, 1, 0, 0, 0, 0,
+	/* 13 */ 1, 1, 0, 0, 0, 0, 0, 0,
 	/* 14 */ 1, 0, 0, 0, 0, 0, 0, 0,
 	/* 15 */ 1, 1, 1, 1, 1, 0, 0, 0,
 	/* 16 */ 0, 0, 0, 0, 0, 0, 0, 0,