diff --git a/reactos/subsystems/win32/win32k/eng/mem.c b/reactos/subsystems/win32/win32k/eng/mem.c
index 8490a11aaf0..7331e1d5805 100644
--- a/reactos/subsystems/win32/win32k/eng/mem.c
+++ b/reactos/subsystems/win32/win32k/eng/mem.c
@@ -72,7 +72,7 @@ EngFreeMem(PVOID Mem)
  * @implemented
  */
 PVOID STDCALL
-EngAllocUserMem(ULONG cj, ULONG Tag)
+EngAllocUserMem(SIZE_T cj, ULONG Tag)
 {
   PVOID NewMem = NULL;
   NTSTATUS Status;