diff --git a/lualib-src/lua-skynet.c b/lualib-src/lua-skynet.c
index fe909a44..1424c92d 100644
--- a/lualib-src/lua-skynet.c
+++ b/lualib-src/lua-skynet.c
@@ -399,6 +399,9 @@ static int
 _trace_new(lua_State *L) {
 	struct trace_pool *p = lua_touserdata(L,1);
 	struct trace_info *t = trace_new(p);
+	if (t==NULL) {
+		return luaL_error(L, "Last trace didn't close");
+	}
 	lua_pushlightuserdata(L,t);
 	return 1;
 }
diff --git a/lualib-src/trace_service.c b/lualib-src/trace_service.c
index 453f2202..23deb40f 100644
--- a/lualib-src/trace_service.c
+++ b/lualib-src/trace_service.c
@@ -81,7 +81,9 @@ trace_release(struct trace_pool *p) {
 
 struct trace_info *
 trace_new(struct trace_pool *p) {
-	assert(p->current == NULL);
+	if (p->current) {
+		return NULL;
+	}
 	struct trace_info *t = malloc(sizeof(*t));
 	p->current = t;
 	t->session = 0;