diff --git a/src/core.sh b/src/core.sh
index 82aba9f..84f3bad 100644
--- a/src/core.sh
+++ b/src/core.sh
@@ -1297,6 +1297,13 @@ get() {
             ;;
         *reality*)
             net=reality
+            [[ $is_reality_fallback ]] && {
+                # If fallback is enabled, we MUST use their Caddy domain
+                [[ ! $is_servername || $is_servername == $is_random_servername ]] && {
+                    msg "\n由于启用了 Caddy 回落，REALITY 必须借用你自己 Caddy 网站的域名和证书才能完成握手。"
+                    ask string is_servername "请输入你在 Caddy 中配置的网站域名:"
+                }
+            }
             [[ ! $is_servername ]] && is_servername=$is_random_servername
             [[ ! $is_private_key ]] && get_pbk
             local handshake_server=$is_servername