diff --git a/ArmPkg/Include/Library/ArmMtlLib.h b/ArmPkg/Include/Library/ArmMtlLib.h
index 4218a741e5..48641258ba 100644
--- a/ArmPkg/Include/Library/ArmMtlLib.h
+++ b/ArmPkg/Include/Library/ArmMtlLib.h
@@ -68,7 +68,7 @@ typedef struct {
 EFI_STATUS
 MtlWaitUntilChannelFree (
   IN MTL_CHANNEL  *Channel,
-  IN UINT64       TimeOutInMicroSeconds
+  IN UINTN        TimeOutInMicroSeconds
   );
 
 /** Return the address of the message payload.