diff --git a/composer.json b/composer.json
index 5bfaacf..d7c2eca 100644
--- a/composer.json
+++ b/composer.json
@@ -22,14 +22,16 @@
   ],
   "require": {
     "php": ">=7.0",
-    "ext-mbstring": "*",
-    "ext-swoole": ">=4.4.19"
+    "ext-mbstring": "*"
   },
   "require-dev": {
     "friendsofphp/php-cs-fixer": "^2.16",
     "phpunit/phpunit": "^7.0.0",
     "swoole/ide-helper": ">=4.4.19"
   },
+  "suggest": {
+    "ext-swoole": "The ext-swoole >= v4.4.19 needs to be loaded when using the MQTT Client."
+  },
   "autoload": {
     "psr-4": {
       "Simps\\MQTT\\": "src/"
diff --git a/docs/en/README.md b/docs/en/README.md
index c8b3889..9d11dad 100644
--- a/docs/en/README.md
+++ b/docs/en/README.md
@@ -9,8 +9,8 @@ Support for `QoS 0`, `QoS 1`, `QoS 2`.
 ## Requirements
 
 * PHP >= `7.0`
-* ext-swoole >= `4.4.19`
 * ext-mbstring
+* [ext-swoole](https://github.com/swoole/swoole-src) >= `4.4.19` (The ext-swoole >= `v4.4.19` needs to be loaded when using [the MQTT Client](/en/client))
 
 ## Install
 
diff --git a/docs/zh-cn/README.md b/docs/zh-cn/README.md
index c816c65..665bb24 100644
--- a/docs/zh-cn/README.md
+++ b/docs/zh-cn/README.md
@@ -7,8 +7,8 @@
 ## 依赖要求
 
 * PHP >= `7.0`
-* Swoole >= `4.4.19`
 * mbstring PHP 扩展
+* [Swoole 扩展](https://github.com/swoole/swoole-src) >= `4.4.19` (使用 [Client](/zh-cn/client) 时需要)
 
 ## 安装