diff --git a/apisix/core/config_etcd.lua b/apisix/core/config_etcd.lua
index 7d25c387eb924..1d88c26b2e5c1 100644
--- a/apisix/core/config_etcd.lua
+++ b/apisix/core/config_etcd.lua
@@ -151,8 +151,10 @@ local function run_watch(premature)
     local rev = 0
     if loaded_configuration then
         local _, res = next(loaded_configuration)
-        rev = tonumber(res.headers["X-Etcd-Index"])
-        assert(rev > 0, 'invalid res.headers["X-Etcd-Index"]')
+        if res then
+            rev = tonumber(res.headers["X-Etcd-Index"])
+            assert(rev > 0, 'invalid res.headers["X-Etcd-Index"]')
+        end
     end
 
     if rev == 0 then