diff --git a/reactos/ntoskrnl/mm/virtual.c b/reactos/ntoskrnl/mm/virtual.c
index 8c199fa5f76..80581b59aad 100644
--- a/reactos/ntoskrnl/mm/virtual.c
+++ b/reactos/ntoskrnl/mm/virtual.c
@@ -1245,9 +1245,9 @@ NTAPI
 NtGetWriteWatch(IN HANDLE ProcessHandle,
                 IN ULONG Flags,
                 IN PVOID BaseAddress,
-                IN ULONG RegionSize,
+                IN SIZE_T RegionSize,
                 IN PVOID *UserAddressArray,
-                OUT PULONG EntriesInUserAddressArray,
+                OUT PULONG_PTR EntriesInUserAddressArray,
                 OUT PULONG Granularity)
 {
     if (!EntriesInUserAddressArray || !Granularity)
@@ -1279,7 +1279,7 @@ NTSTATUS
 NTAPI
 NtResetWriteWatch(IN HANDLE ProcessHandle,
                   IN PVOID BaseAddress,
-                  IN ULONG RegionSize)
+                  IN SIZE_T RegionSize)
 {
     if (!RegionSize)
     {