diff --git a/src/networking.c b/src/networking.c
index 915a0b016..f39df9d95 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -1775,6 +1775,7 @@ void freeClient(client *c) {
 void freeClientAsync(client *c) {
     if (c->flag.close_asap || c->flag.script) return;
     c->flag.close_asap = 1;
+    debugServerAssertWithInfo(c, NULL, listSearchKey(server.clients_to_close, c) == NULL);
     listAddNodeTail(server.clients_to_close, c);
 }