diff --git a/CHANGELOG.md b/CHANGELOG.md
index b95426bb..a2f49a60 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@
 * Builtin Prosody: list existing rooms in the settings page
 * Builtin Prosody: new settings to enable local C2S. For example, can be used with Matterbridge (thanks https://github.com/tytan652)
 
+### Fixes
+
+* Fix broken API diagnostic.
+
 ## v3.1.0
 
 ### Features
diff --git a/server/lib/diagnostic/prosody.ts b/server/lib/diagnostic/prosody.ts
index f069eb54..64b0fe70 100644
--- a/server/lib/diagnostic/prosody.ts
+++ b/server/lib/diagnostic/prosody.ts
@@ -21,12 +21,14 @@ export async function diagProsody (test: string, options: RegisterServerOptions)
   // FIXME: these tests are very similar to tests in testProsodyCorrectlyRunning. Remove from here?
   // Testing the prosody config file.
   let prosodyPort: string
+  let prosodyHost: string
   try {
     const wantedConfig = await getProsodyConfig(options)
     const filePath = wantedConfig.paths.config
 
     result.messages.push(`Prosody will run on port '${wantedConfig.port}'`)
     prosodyPort = wantedConfig.port
+    prosodyHost = wantedConfig.host
 
     result.messages.push(`Prosody will use ${wantedConfig.baseApiUrl} as base uri from api calls`)
 
@@ -99,7 +101,8 @@ export async function diagProsody (test: string, options: RegisterServerOptions)
     const testResult = await got(apiUrl, {
       method: 'GET',
       headers: {
-        authorization: 'Bearer ' + await getAPIKey(options)
+        authorization: 'Bearer ' + await getAPIKey(options),
+        host: prosodyHost
       },
       responseType: 'json',
       resolveBodyOnly: true
@@ -120,7 +123,8 @@ export async function diagProsody (test: string, options: RegisterServerOptions)
     const testResult = await got(apiUrl, {
       method: 'GET',
       headers: {
-        authorization: 'Bearer ' + await getAPIKey(options)
+        authorization: 'Bearer ' + await getAPIKey(options),
+        host: prosodyHost
       },
       responseType: 'json',
       resolveBodyOnly: true
diff --git a/server/lib/prosody/config.ts b/server/lib/prosody/config.ts
index 1c077845..ac7d4819 100644
--- a/server/lib/prosody/config.ts
+++ b/server/lib/prosody/config.ts
@@ -66,6 +66,7 @@ async function getProsodyFilePaths (options: RegisterServerOptions): Promise<Pro
 interface ProsodyConfig {
   content: string
   paths: ProsodyFilePaths
+  host: string
   port: string
   baseApiUrl: string
 }
@@ -137,7 +138,8 @@ async function getProsodyConfig (options: RegisterServerOptions): Promise<Prosod
     content,
     paths,
     port,
-    baseApiUrl
+    baseApiUrl,
+    host: prosodyDomain
   }
 }
 
diff --git a/server/lib/prosody/config/content.ts b/server/lib/prosody/config/content.ts
index 6fb0f107..6d1664ff 100644
--- a/server/lib/prosody/config/content.ts
+++ b/server/lib/prosody/config/content.ts
@@ -248,9 +248,9 @@ class ProsodyConfigContent {
   }
 
   useTestModule (prosodyApikey: string, apiurl: string): void {
-    this.global.add('modules_enabled', 'http_peertubelivechat_test')
-    this.global.set('peertubelivechat_test_apikey', prosodyApikey)
-    this.global.set('peertubelivechat_test_peertube_api_url', apiurl)
+    this.muc.add('modules_enabled', 'http_peertubelivechat_test')
+    this.muc.set('peertubelivechat_test_apikey', prosodyApikey)
+    this.muc.set('peertubelivechat_test_peertube_api_url', apiurl)
   }
 
   setLog (level: ProsodyLogLevel, syslog?: ProsodyLogLevel[]): void {
diff --git a/server/lib/prosody/ctl.ts b/server/lib/prosody/ctl.ts
index dd033ed2..19c9e2fe 100644
--- a/server/lib/prosody/ctl.ts
+++ b/server/lib/prosody/ctl.ts
@@ -195,7 +195,10 @@ async function ensureProsodyRunning (options: RegisterServerOptions): Promise<vo
   })
 
   // Set the http-bind route.
-  changeHttpBindRoute(options, config.port)
+  changeHttpBindRoute(options, {
+    host: config.host,
+    port: config.port
+  })
 
   async function sleep (ms: number): Promise<any> {
     return new Promise((resolve) => {
diff --git a/server/lib/routers/webchat.ts b/server/lib/routers/webchat.ts
index 8b67417d..aa23019c 100644
--- a/server/lib/routers/webchat.ts
+++ b/server/lib/routers/webchat.ts
@@ -13,7 +13,11 @@ const fs = require('fs').promises
 const proxy = require('express-http-proxy')
 
 let httpBindRoute: RequestHandler
-let prosodyPort: string | undefined
+interface ProsodyHttpBindInfo {
+  host: string
+  port: string
+}
+let currentProsodyHttpBindInfo: ProsodyHttpBindInfo | null = null
 
 async function initWebchatRouter (options: RegisterServerOptions): Promise<Router> {
   const {
@@ -124,15 +128,16 @@ async function initWebchatRouter (options: RegisterServerOptions): Promise<Route
         return
       }
 
-      if (!prosodyPort) {
+      if (!currentProsodyHttpBindInfo) {
         throw new Error('It seems that prosody is not binded... Cant list rooms.')
       }
-      const apiUrl = `http://localhost:${prosodyPort}/peertubelivechat_list_rooms/list-rooms`
+      const apiUrl = `http://localhost:${currentProsodyHttpBindInfo.port}/peertubelivechat_list_rooms/list-rooms`
       peertubeHelpers.logger.debug('Calling list rooms API on url: ' + apiUrl)
       const rooms = await got(apiUrl, {
         method: 'GET',
         headers: {
-          authorization: 'Bearer ' + await getAPIKey(options)
+          authorization: 'Bearer ' + await getAPIKey(options),
+          host: currentProsodyHttpBindInfo.host
         },
         responseType: 'json',
         resolveBodyOnly: true
@@ -150,20 +155,25 @@ async function initWebchatRouter (options: RegisterServerOptions): Promise<Route
   return router
 }
 
-function changeHttpBindRoute ({ peertubeHelpers }: RegisterServerOptions, port: string | null): void {
+function changeHttpBindRoute (
+  { peertubeHelpers }: RegisterServerOptions,
+  prosodyHttpBindInfo: ProsodyHttpBindInfo | null
+): void {
   const logger = peertubeHelpers.logger
-  logger.info('Changing http-bind port for ' + (port ?? 'null'))
-  if (port !== null && !/^\d+$/.test(port)) {
-    logger.error('Port is not valid. Replacing by null')
-    port = null
+  if (prosodyHttpBindInfo && !/^\d+$/.test(prosodyHttpBindInfo.port)) {
+    logger.error(`Port '${prosodyHttpBindInfo.port}' is not valid. Replacing by null`)
+    prosodyHttpBindInfo = null
   }
-  if (port === null) {
-    prosodyPort = undefined
+
+  if (!prosodyHttpBindInfo) {
+    logger.info('Changing http-bind port for null')
+    currentProsodyHttpBindInfo = null
     httpBindRoute = (_req: Request, res: Response, _next: NextFunction) => {
       res.status(404)
       res.send('Not found')
     }
   } else {
+    logger.info('Changing http-bind port for ' + prosodyHttpBindInfo.port + ', on host ' + prosodyHttpBindInfo.host)
     const options: ProxyOptions = {
       https: false,
       proxyReqPathResolver: async (_req: Request): Promise<string> => {
@@ -173,8 +183,8 @@ function changeHttpBindRoute ({ peertubeHelpers }: RegisterServerOptions, port:
       parseReqBody: true // Note that setting this to false overrides reqAsBuffer and reqBodyEncoding below.
       // FIXME: should we remove cookies?
     }
-    prosodyPort = port
-    httpBindRoute = proxy('http://localhost:' + port, options)
+    currentProsodyHttpBindInfo = prosodyHttpBindInfo
+    httpBindRoute = proxy('http://localhost:' + prosodyHttpBindInfo.port, options)
   }
 }