diff --git a/ntoskrnl/ex/uuid.c b/ntoskrnl/ex/uuid.c
index 1f41bdb1227..8c8270a3db9 100644
--- a/ntoskrnl/ex/uuid.c
+++ b/ntoskrnl/ex/uuid.c
@@ -261,7 +261,7 @@ ExpAllocateUuids(PULARGE_INTEGER Time,
     else
     {
         *Range = TIME_FRAME;
-        ClockDiff.QuadPart -= TIME_FRAME;
+        ClockDiff.QuadPart = TimeDiff.QuadPart - TIME_FRAME;
         --ClockDiff.HighPart;
     }