diff --git a/reactos/hal/halx86/generic/memory.c b/reactos/hal/halx86/generic/memory.c
index 7e52c23fb25..1422306f936 100644
--- a/reactos/hal/halx86/generic/memory.c
+++ b/reactos/hal/halx86/generic/memory.c
@@ -190,7 +190,7 @@ HalpMapPhysicalMemory64(IN PHYSICAL_ADDRESS PhysicalAddress,
     {
         /* Fill out the PTE */
         PointerPte = HalAddressToPte(BaseAddress);
-        PointerPte->PageFrameNumber = (ULONG_PTR)PhysicalAddress.QuadPart >> PAGE_SHIFT;
+        PointerPte->PageFrameNumber = (PFN_NUMBER)(PhysicalAddress.QuadPart >> PAGE_SHIFT);
         PointerPte->Valid = 1;
         PointerPte->Write = 1;