diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index d94da24f42..f34863e0df 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -729,7 +729,7 @@ void hpet_disable_legacy_broadcast(void)
 
     spin_lock_irqsave(&hpet_events->lock, flags);
 
-    hpet_events->flags |= HPET_EVT_DISABLE;
+    set_bit(HPET_EVT_DISABLE_BIT, &hpet_events->flags);
 
     /* disable HPET T0 */
     cfg = hpet_read32(HPET_Tn_CFG(0));