diff --git a/CHANGES b/CHANGES
index 30ef721a7..decc39c70 100644
--- a/CHANGES
+++ b/CHANGES
@@ -29,6 +29,7 @@ Bugfixes:
  - GB: Properly initialize sramRealVf variable
  - Qt: Fix Apply button for key and controller configurations
  - GB Video: Initialize LCDC in renderer
+ - GBA I/O: Mask off WAITCNT bits that cannot be written
 Misc:
  - PSP2: Improved controller rumble
  - GB, GBA: Prevent loading null ROMs
diff --git a/src/gba/io.c b/src/gba/io.c
index 75e8689bf..2a7fdc5b1 100644
--- a/src/gba/io.c
+++ b/src/gba/io.c
@@ -530,6 +530,7 @@ void GBAIOWrite(struct GBA* gba, uint32_t address, uint16_t value) {
 
 		// Interrupts and misc
 		case REG_WAITCNT:
+			value &= 0x5FFF;
 			GBAAdjustWaitstates(gba, value);
 			break;
 		case REG_IE: