diff --git a/src/GBACartMotionPak.cpp b/src/GBACartMotionPak.cpp
index 047b0f97..44743464 100644
--- a/src/GBACartMotionPak.cpp
+++ b/src/GBACartMotionPak.cpp
@@ -161,6 +161,7 @@ void CartMotionPakRetail::DoSavestate(Savestate* file)
 
 u16 CartMotionPakRetail::ROMRead(u32 addr) const
 {
+    // CHECKME: Retail cartridge seems to return 0x7C7C.
     return 0xFCFF;
 }