diff --git a/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/http/router/base.kt b/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/http/router/base.kt
index 366bd1e1..966d5815 100644
--- a/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/http/router/base.kt
+++ b/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/http/router/base.kt
@@ -9,7 +9,9 @@
 
 package net.mamoe.mirai.api.http.adapter.http.router
 
+import io.ktor.serialization.kotlinx.json.*
 import io.ktor.server.application.*
+import io.ktor.server.plugins.contentnegotiation.*
 import io.ktor.server.plugins.cors.routing.*
 import io.ktor.server.plugins.defaultheaders.*
 import io.ktor.server.plugins.doublereceive.*
@@ -17,6 +19,7 @@ import net.mamoe.mirai.api.http.adapter.http.HttpAdapter
 import net.mamoe.mirai.api.http.adapter.http.plugin.Authorization
 import net.mamoe.mirai.api.http.adapter.http.plugin.GlobalExceptionHandler
 import net.mamoe.mirai.api.http.adapter.http.plugin.HttpRouterMonitor
+import net.mamoe.mirai.api.http.adapter.internal.serializer.BuiltinJsonSerializer
 import net.mamoe.mirai.api.http.context.MahContextHolder
 
 
@@ -31,6 +34,7 @@ fun Application.httpModule(adapter: HttpAdapter) {
         }
     }
 
+    install(ContentNegotiation) { json(json = BuiltinJsonSerializer.buildJson()) }
     install(GlobalExceptionHandler)
     install(Authorization)
     if (MahContextHolder.debug) {
diff --git a/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/internal/serializer/BuiltinJson.kt b/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/internal/serializer/BuiltinJson.kt
index 1699c75b..6724af0a 100644
--- a/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/internal/serializer/BuiltinJson.kt
+++ b/mirai-api-http/src/main/kotlin/net/mamoe/mirai/api/http/adapter/internal/serializer/BuiltinJson.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 Mamoe Technologies and contributors.
+ * Copyright 2023 Mamoe Technologies and contributors.
  *
  * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
  * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
@@ -22,11 +22,8 @@ import kotlin.reflect.KClass
 @OptIn(InternalSerializationApi::class)
 internal class BuiltinJsonSerializer : InternalSerializer {
 
-    /**
-     * Json解析规则，需要注册支持的多态的类
-     */
-    private val json by lazy {
-        Json {
+    companion object {
+        fun buildJson() = Json {
             encodeDefaults = true
             isLenient = true
             ignoreUnknownKeys = true
@@ -36,22 +33,27 @@ internal class BuiltinJsonSerializer : InternalSerializer {
                 polymorphicSealedClass(EventDTO::class, BotEventDTO::class)
             }
         }
+
+        /**
+         * 从 sealed class 里注册到多态序列化
+         */
+        @InternalSerializationApi
+        @Suppress("UNCHECKED_CAST")
+        private fun <B : Any, S : B> SerializersModuleBuilder.polymorphicSealedClass(
+            baseClass: KClass<B>,
+            sealedClass: KClass<S>
+        ) {
+            sealedClass.sealedSubclasses.forEach {
+                val c = it as KClass<S>
+                polymorphic(baseClass, c, c.serializer())
+            }
+        }
     }
 
     /**
-     * 从 sealed class 里注册到多态序列化
+     * Json解析规则，需要注册支持的多态的类
      */
-    @InternalSerializationApi
-    @Suppress("UNCHECKED_CAST")
-    private fun <B : Any, S : B> SerializersModuleBuilder.polymorphicSealedClass(
-        baseClass: KClass<B>,
-        sealedClass: KClass<S>
-    ) {
-        sealedClass.sealedSubclasses.forEach {
-            val c = it as KClass<S>
-            polymorphic(baseClass, c, c.serializer())
-        }
-    }
+    private val json by lazy { buildJson()  }
 
     override fun <T : Any> encode(dto: T, clazz: KClass<T>): String = when (dto) {
         is StateCode -> json.encodeToString(StateCode.serializer(), dto)
diff --git a/mirai-api-http/src/test/kotlin/framework/TestMahApplication.kt b/mirai-api-http/src/test/kotlin/framework/TestMahApplication.kt
index b37656bb..2775729a 100644
--- a/mirai-api-http/src/test/kotlin/framework/TestMahApplication.kt
+++ b/mirai-api-http/src/test/kotlin/framework/TestMahApplication.kt
@@ -1,3 +1,12 @@
+/*
+ * Copyright 2023 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
 package framework
 
 import io.ktor.client.*
@@ -19,6 +28,7 @@ import kotlinx.serialization.json.Json
 import net.mamoe.mirai.api.http.adapter.MahAdapter
 import net.mamoe.mirai.api.http.adapter.MahAdapterFactory
 import net.mamoe.mirai.api.http.adapter.http.router.httpModule
+import net.mamoe.mirai.api.http.adapter.internal.serializer.BuiltinJsonSerializer
 import net.mamoe.mirai.api.http.adapter.webhook.WebhookAdapter
 import net.mamoe.mirai.api.http.adapter.ws.router.websocketRouteModule
 import net.mamoe.mirai.api.http.context.MahContextHolder
@@ -70,7 +80,7 @@ class MahApplicationTestBuilder(private val builder: ApplicationTestBuilder): Cl
             contentConverter = KotlinxWebsocketSerializationConverter(Json)
         }
         install(ContentNegotiation) {
-            json(json = buildPolyJson())
+            json(json = BuiltinJsonSerializer.buildJson())
         }
     }}
 
diff --git a/mirai-api-http/src/test/kotlin/framework/json.kt b/mirai-api-http/src/test/kotlin/framework/json.kt
deleted file mode 100644
index cb8f43f6..00000000
--- a/mirai-api-http/src/test/kotlin/framework/json.kt
+++ /dev/null
@@ -1,34 +0,0 @@
-package framework
-
-import kotlinx.serialization.InternalSerializationApi
-import kotlinx.serialization.json.Json
-import kotlinx.serialization.modules.SerializersModule
-import kotlinx.serialization.modules.SerializersModuleBuilder
-import kotlinx.serialization.serializer
-import net.mamoe.mirai.api.http.adapter.internal.dto.BotEventDTO
-import net.mamoe.mirai.api.http.adapter.internal.dto.EventDTO
-import net.mamoe.mirai.api.http.adapter.internal.dto.MessagePacketDTO
-import kotlin.reflect.KClass
-
-
-fun buildPolyJson() = Json {
-    serializersModule = SerializersModule {
-        polymorphicSealedClass(EventDTO::class, MessagePacketDTO::class)
-        polymorphicSealedClass(EventDTO::class, BotEventDTO::class)
-    }
-}
-
-/**
- * 从 sealed class 里注册到多态序列化
- */
-@OptIn(InternalSerializationApi::class)
-@Suppress("UNCHECKED_CAST")
-private fun <B : Any, S : B> SerializersModuleBuilder.polymorphicSealedClass(
-    baseClass: KClass<B>,
-    sealedClass: KClass<S>
-) {
-    sealedClass.sealedSubclasses.forEach {
-        val c = it as KClass<S>
-        polymorphic(baseClass, c, c.serializer())
-    }
-}
\ No newline at end of file