diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
index fdcda2be1b..5bff073bc5 100644
--- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
+++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
@@ -33,10 +33,14 @@
    It is therefore stored here. 0 means the timer is not running. */
 STATIC UINT64  mTimerPeriod = 0;
 
+/* disables watchdog interaction after Exit Boot Services */
+STATIC BOOLEAN  mExitedBootServices = FALSE;
+
 #define MAX_UINT48  0xFFFFFFFFFFFFULL
 
 STATIC EFI_HARDWARE_INTERRUPT2_PROTOCOL  *mInterruptProtocol;
 STATIC EFI_WATCHDOG_TIMER_NOTIFY         mWatchdogNotify;
+STATIC EFI_EVENT                         mEfiExitBootServicesEvent;
 
 /**
   This function returns the maximum watchdog offset register value.
@@ -118,7 +122,8 @@ WatchdogExitBootServicesEvent (
   )
 {
   WatchdogDisable ();
-  mTimerPeriod = 0;
+  mTimerPeriod        = 0;
+  mExitedBootServices = TRUE;
 }
 
 /* This function is called when the watchdog's first signal (WS0) goes high.
@@ -215,6 +220,8 @@ WatchdogRegisterHandler (
 
   @retval EFI_SUCCESS           The watchdog timer has been programmed to fire
                                 in TimerPeriod 100ns units.
+  @retval EFI_DEVICE_ERROR      Boot Services has been exited but TimerPeriod
+                                is not zero.
 
 **/
 STATIC
@@ -230,7 +237,15 @@ WatchdogSetTimerPeriod (
   UINT64  TimerFrequencyHz;
   UINT64  NumTimerTicks;
 
-  // if TimerPeriod is 0, this is a request to stop the watchdog.
+  // If we've exited Boot Services but TimerPeriod isn't zero, this
+  // indicates that the caller is doing something wrong.
+  if (mExitedBootServices && (TimerPeriod != 0)) {
+    mTimerPeriod = 0;
+    WatchdogDisable ();
+    return EFI_DEVICE_ERROR;
+  }
+
+  // If TimerPeriod is 0 this is a request to stop the watchdog.
   if (TimerPeriod == 0) {
     mTimerPeriod = 0;
     WatchdogDisable ();
@@ -335,8 +350,6 @@ STATIC EFI_WATCHDOG_TIMER_ARCH_PROTOCOL  mWatchdogTimer = {
   WatchdogGetTimerPeriod
 };
 
-STATIC EFI_EVENT  mEfiExitBootServicesEvent;
-
 EFI_STATUS
 EFIAPI
 GenericWatchdogEntry (