diff --git a/apisix/plugin.lua b/apisix/plugin.lua
index efdffe47d40e..b1b7d660c440 100644
--- a/apisix/plugin.lua
+++ b/apisix/plugin.lua
@@ -264,7 +264,7 @@ function _M.load(config)
         local_conf, err = core.config.local_conf(true)
         if not local_conf then
             -- the error is unrecoverable, so we need to raise it
-            error("failed to load the configuration file: ", err)
+            error("failed to load the configuration file: " .. err)
         end
 
         http_plugin_names = local_conf.plugins