diff --git a/Source/Core/Core/IOS/STM/STM.cpp b/Source/Core/Core/IOS/STM/STM.cpp
index 06571b4ae3..e262fc4001 100644
--- a/Source/Core/Core/IOS/STM/STM.cpp
+++ b/Source/Core/Core/IOS/STM/STM.cpp
@@ -65,6 +65,7 @@ std::optional<IPCReply> STMImmediateDevice::IOCtl(const IOCtlRequest& request)
   case IOCTL_STM_READDDRREG2:
   case IOCTL_STM_LEDFLASH:
   case IOCTL_STM_READVER:
+  case IOCTL_STM_WRITEDMCU:
     ERROR_LOG_FMT(IOS_STM, "{} - Unimplemented IOCtl: {}", GetDeviceName(), request.request);
     break;
 
diff --git a/Source/Core/Core/IOS/STM/STM.h b/Source/Core/Core/IOS/STM/STM.h
index ae2068b792..f249c66d95 100644
--- a/Source/Core/Core/IOS/STM/STM.h
+++ b/Source/Core/Core/IOS/STM/STM.h
@@ -32,6 +32,7 @@ enum
   IOCTL_STM_LEDFLASH = 0x6001,
   IOCTL_STM_LEDMODE = 0x6002,
   IOCTL_STM_READVER = 0x7001,
+  IOCTL_STM_WRITEDMCU = 0x8001,
 };
 
 enum