diff --git a/mxshadowsrv.c b/mxshadowsrv.c
index 7e4614b..b8af131 100644
--- a/mxshadowsrv.c
+++ b/mxshadowsrv.c
@@ -193,7 +193,7 @@ static void *client_thread(void *arg) {
 
     while (1) {
 #ifdef DEBUG_MAX_CONNECTS
-        if ( __sync_fetch_and_sub(&debug_remaining_connects, 1) <= 0)
+        if ( __atomic_fetch_sub(&debug_remaining_connects, 1, __ATOMIC_RELAXED) <= 0)
             return NULL;
 #endif
         int _cleanup_(free_fd) socket = accept4(listen_socket, NULL, NULL, SOCK_NONBLOCK);