diff --git a/src/ngx_http_lua_kong_request_id.c b/src/ngx_http_lua_kong_request_id.c
index 94245ab0..fe8161a4 100644
--- a/src/ngx_http_lua_kong_request_id.c
+++ b/src/ngx_http_lua_kong_request_id.c
@@ -22,6 +22,21 @@
 #define KONG_REQUEST_ID_FORMAT      "%08xD%08xD%08xD%08xD"
 
 
+static ngx_int_t
+ngx_http_lua_kong_variable_request_id(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
+
+
+static ngx_http_variable_t  ngx_http_lua_kong_variables[] = {
+
+    { ngx_string("kong_request_id"), NULL,
+      ngx_http_lua_kong_variable_request_id,
+      0, 0, 0 },
+
+      ngx_http_null_variable
+};
+
+
 static ngx_int_t
 ngx_http_lua_kong_variable_request_id(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data)
@@ -48,3 +63,21 @@ ngx_http_lua_kong_variable_request_id(ngx_http_request_t *r,
 }
 
 
+ngx_int_t
+ngx_http_lua_kong_add_vars(ngx_conf_t *cf)
+{
+    ngx_http_variable_t        *cv, *v;
+
+    for (cv = ngx_http_lua_kong_variables; cv->name.len; cv++) {
+        v = ngx_http_add_variable(cf, &cv->name, cv->flags);
+        if (v == NULL) {
+            return NGX_ERROR;
+        }
+
+        *v = *cv;
+    }
+
+    return NGX_OK;
+}
+
+