diff --git a/sys/ia64/ia64/mp_machdep.c b/sys/ia64/ia64/mp_machdep.c
index ce2b4d1c8754..6885286f86ff 100644
--- a/sys/ia64/ia64/mp_machdep.c
+++ b/sys/ia64/ia64/mp_machdep.c
@@ -125,7 +125,7 @@ ia64_ap_startup(void)
 	ia64_mca_save_state(SAL_INFO_MCA);
 	ia64_mca_save_state(SAL_INFO_CMC);
 
-	ap_awake++;
+	atomic_add_int(&ap_awake, 1);
 	while (!smp_started)
 		cpu_spinwait();