diff --git a/web/html/form/outbound.html b/web/html/form/outbound.html
index a2de920a..21bc11fc 100644
--- a/web/html/form/outbound.html
+++ b/web/html/form/outbound.html
@@ -612,7 +612,7 @@
             </a-divider>
             <a-form-item label='Type'>
               <a-select v-model="mask.type"
-                @change="(type) => mask.settings = mask._getDefaultSettings(type, {})"
+                @change="(type) => { mask.settings = mask._getDefaultSettings(type, {}); if(outbound.stream.network === 'kcp') { outbound.stream.kcp.mtu = type === 'xdns' ? 900 : 1350; } }"
                 :dropdown-class-name="themeSwitcher.currentTheme">
                 <!-- Salamander for Hysteria2 only -->
                 <a-select-option v-if="outbound.protocol === Protocols.Hysteria"
@@ -643,9 +643,9 @@
                 <a-select-option v-if="outbound.stream.network === 'kcp'"
                   value="mkcp-original">
                   mKCP Original</a-select-option>
-                <!-- xDNS for TCP/WS/HTTPUpgrade/XHTTP -->
+                <!-- xDNS for TCP/WS/HTTPUpgrade/XHTTP/KCP -->
                 <a-select-option
-                  v-if="['tcp', 'ws', 'httpupgrade', 'xhttp'].includes(outbound.stream.network)"
+                  v-if="['tcp', 'ws', 'httpupgrade', 'xhttp', 'kcp'].includes(outbound.stream.network)"
                   value="xdns">
                   xDNS (Experimental)</a-select-option>
               </a-select>
diff --git a/web/html/form/stream/stream_finalmask.html b/web/html/form/stream/stream_finalmask.html
index 35962dfa..0b6418b7 100644
--- a/web/html/form/stream/stream_finalmask.html
+++ b/web/html/form/stream/stream_finalmask.html
@@ -18,7 +18,7 @@
             </a-divider>
             <a-form-item label='Type'>
                 <a-select v-model="mask.type"
-                    @change="(type) => mask.settings = mask._getDefaultSettings(type, {})"
+                    @change="(type) => { mask.settings = mask._getDefaultSettings(type, {}); if(inbound.stream.network === 'kcp') { inbound.stream.kcp.mtu = type === 'xdns' ? 900 : 1350; } }"
                     :dropdown-class-name="themeSwitcher.currentTheme">
                     <!-- mKCP-specific masks -->
                     <a-select-option v-if="inbound.stream.network === 'kcp'"
@@ -48,9 +48,9 @@
                     <a-select-option v-if="inbound.stream.network === 'kcp'"
                         value="xicmp">
                         xICMP (Experimental)</a-select-option>
-                    <!-- xDNS for TCP/WS/HTTPUpgrade/XHTTP -->
+                    <!-- xDNS for TCP/WS/HTTPUpgrade/XHTTP/KCP -->
                     <a-select-option
-                        v-if="['tcp', 'ws', 'httpupgrade', 'xhttp'].includes(inbound.stream.network)"
+                        v-if="['tcp', 'ws', 'httpupgrade', 'xhttp', 'kcp'].includes(inbound.stream.network)"
                         value="xdns">
                         xDNS (Experimental)</a-select-option>
                 </a-select>