diff --git a/core/fiber.m b/core/fiber.m
index c1bc0755767bb3361cbe707ec5291861ceb610fe..0b9cb25d10bb39a6acba8a8b6faa796ba7a52245 100644
--- a/core/fiber.m
+++ b/core/fiber.m
@@ -64,8 +64,6 @@ static struct fiber **sp, *call_stack[64];
 static uint32_t last_used_fid;
 static struct palloc_pool *ex_pool;
 
-static uint32_t watermark = 0;
-
 struct fiber_cleanup {
 	void (*handler) (void *data);
 	void *data;
@@ -1227,7 +1225,7 @@ void
 fiber_init(void)
 {
 	SLIST_INIT(&fibers);
-	fibers_registry = kh_init(fid2fiber, &watermark);
+	fibers_registry = kh_init(fid2fiber, NULL);
 
 	ex_pool = palloc_create_pool("ex_pool");