diff --git a/CHANGES b/CHANGES
index e4a87bdf6..3e7ad3932 100644
--- a/CHANGES
+++ b/CHANGES
@@ -40,6 +40,7 @@ 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:
  - SDL: Remove scancode key input
  - GBA Video: Clean up unused timers
diff --git a/src/gba/io.c b/src/gba/io.c
index fe4262f6c..6aa68a8b9 100644
--- a/src/gba/io.c
+++ b/src/gba/io.c
@@ -535,6 +535,7 @@ 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: