diff --git a/kern/start.c b/kern/start.c
index 7d0e855..a8175c2 100644
--- a/kern/start.c
+++ b/kern/start.c
@@ -30,8 +30,7 @@ volatile int max_hart = 0;
 /* This is where entry.S drops us of. All cores land here */
 void start() {
     // Do this first
-    __sync_fetch_and_add(&max_hart, 1);
-    __sync_synchronize();
+    __atomic_fetch_add(&max_hart, 1, __ATOMIC_SEQ_CST);
 
     u64 id = read_mhartid();