diff --git a/plugins/mqtt/mqtt.json b/plugins/mqtt/mqtt.json
index d4ddbf06..989989b2 100644
--- a/plugins/mqtt/mqtt.json
+++ b/plugins/mqtt/mqtt.json
@@ -243,20 +243,5 @@
     "valid": {
       "length": 81960
     }
-  },
-  "keypass": {
-    "name": "Client Private Key Password",
-    "name_zh": "客户端私钥密码",
-    "description": "Client private key password when using two way authentication with an encrypted client private key",
-    "description_zh": "使用加密的客户端私钥进行双向认证时，客户端私钥的密码",
-    "attribute": "optional",
-    "type": "string",
-    "condition": {
-      "field": "ssl",
-      "value": true
-    },
-    "valid": {
-      "length": 256
-    }
   }
 }
diff --git a/plugins/mqtt/mqtt_config.c b/plugins/mqtt/mqtt_config.c
index 2aef69b9..9a4b54e3 100644
--- a/plugins/mqtt/mqtt_config.c
+++ b/plugins/mqtt/mqtt_config.c
@@ -110,6 +110,7 @@ static inline int parse_ssl_params(neu_plugin_t *plugin, const char *setting,
     }
 
     // keypass, optional
+    // keep it here for backward compatibility with version 2.5
     ret = neu_parse_param(setting, NULL, 1, keypass);
     if (0 != ret) {
         plog_notice(plugin, "setting no keypass");
diff --git a/plugins/mqtt/mqtt_config.h b/plugins/mqtt/mqtt_config.h
index ec6e68e2..05f729ca 100644
--- a/plugins/mqtt/mqtt_config.h
+++ b/plugins/mqtt/mqtt_config.h
@@ -66,6 +66,8 @@ typedef struct {
     char *               cert;                // client cert
     char *               key;                 // client key
     char *               keypass;             // client key password
+                                              // remove in 2.6, keep it here
+                                              // for backward compatibility
 } mqtt_config_t;
 
 int  mqtt_config_parse(neu_plugin_t *plugin, const char *setting,