diff --git a/apisix/plugins/skywalking.lua b/apisix/plugins/skywalking.lua
index b9fe013ae6821..f95286bd8d143 100644
--- a/apisix/plugins/skywalking.lua
+++ b/apisix/plugins/skywalking.lua
@@ -16,6 +16,7 @@
 --
 local core = require("apisix.core")
 local ngx = ngx
+local math = math
 
 local sw_client = require("apisix.plugins.skywalking.client")
 local sw_tracer = require("apisix.plugins.skywalking.tracer")