diff --git a/PcAtChipsetPkg/HpetTimerDxe/HpetTimer.c b/PcAtChipsetPkg/HpetTimerDxe/HpetTimer.c
index 427572c2ff..e74777fbc6 100644
--- a/PcAtChipsetPkg/HpetTimerDxe/HpetTimer.c
+++ b/PcAtChipsetPkg/HpetTimerDxe/HpetTimer.c
@@ -387,11 +387,18 @@ TimerInterruptHandler (
                     100000000
                     );
 
+    //
+    // Save main counter value before calling notification function
+    // that may enable interrupts and allow interrupt nesting.
+    //
+    mPreviousMainCounter = MainCounter;
+
     //
     // Call registered notification function passing in the time since the last
     // interrupt in 100 ns units.
     //
     mTimerNotifyFunction (TimerPeriod);
+    return;
   }
 
   //