diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
index a75bdf878..3d186de9d 100644
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -114,11 +114,13 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
     ngx_cpystrn(cycle->conf_file.data, old_cycle->conf_file.data,
                 old_cycle->conf_file.len + 1);
 
-    cycle->conf_param.len = old_cycle->conf_param.len;
-    cycle->conf_param.data = ngx_pstrdup(pool, &old_cycle->conf_param);
-    if (cycle->conf_param.data == NULL) {
-        ngx_destroy_pool(pool);
-        return NULL;
+    if (old_cycle->conf_param.data != NULL) {
+        cycle->conf_param.len = old_cycle->conf_param.len;
+        cycle->conf_param.data = ngx_pstrdup(pool, &old_cycle->conf_param);
+        if (cycle->conf_param.data == NULL) {
+            ngx_destroy_pool(pool);
+            return NULL;
+        }
     }