diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0dbc3715..8671b130 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Features
 
+* Builtin Prosody: optional settings to change the url for Prosody's API calls.
 * Diagnostic tool: testing API communication from Peertube to Prosody.
 * Diagnostic tool: testing API communication from Prosody to Peertube.
 
diff --git a/client/admin-plugin-client-plugin.ts b/client/admin-plugin-client-plugin.ts
index 163b5c0d..c86b7eeb 100644
--- a/client/admin-plugin-client-plugin.ts
+++ b/client/admin-plugin-client-plugin.ts
@@ -40,6 +40,7 @@ function register ({ registerHook, registerSettingsScript, peertubeHelpers }: Re
         case 'chat-type-help-disabled':
           return options.formValues['chat-type'] !== ('disabled' as ChatType)
         case 'prosody-port':
+        case 'prosody-peertube-uri':
         case 'chat-type-help-builtin-prosody':
           return options.formValues['chat-type'] !== ('builtin-prosody' as ChatType)
         case 'chat-server':
diff --git a/server/lib/diagnostic/prosody.ts b/server/lib/diagnostic/prosody.ts
index 1cb2bea3..4fb84785 100644
--- a/server/lib/diagnostic/prosody.ts
+++ b/server/lib/diagnostic/prosody.ts
@@ -28,6 +28,8 @@ export async function diagProsody (test: string, options: RegisterServerOptions)
     result.messages.push(`Prosody will run on port '${wantedConfig.port}'`)
     prosodyPort = wantedConfig.port
 
+    result.messages.push(`Prosody will use ${wantedConfig.baseApiUrl} as base uri from api calls`)
+
     result.messages.push(`Prosody modules path will be '${wantedConfig.paths.modules}'`)
 
     await fs.promises.access(filePath, fs.constants.R_OK) // throw an error if file does not exist.
diff --git a/server/lib/prosody/config.ts b/server/lib/prosody/config.ts
index 5ee2afc1..cf37a8a0 100644
--- a/server/lib/prosody/config.ts
+++ b/server/lib/prosody/config.ts
@@ -67,6 +67,7 @@ interface ProsodyConfig {
   content: string
   paths: ProsodyFilePaths
   port: string
+  baseApiUrl: string
 }
 async function getProsodyConfig (options: RegisterServerOptions): Promise<ProsodyConfig> {
   const logger = options.peertubeHelpers.logger
@@ -80,9 +81,15 @@ async function getProsodyConfig (options: RegisterServerOptions): Promise<Prosod
   const paths = await getProsodyFilePaths(options)
 
   const apikey = await getAPIKey(options)
-  const baseApiUrl = options.peertubeHelpers.config.getWebserverUrl() +
-    getBaseRouterRoute(options) +
-    'api/'
+  let baseApiUrl = await options.settingsManager.getSetting('prosody-peertube-uri') as string
+  if (baseApiUrl && !/^https?:\/\/[a-z0-9.-_]+(?::\d+)?$/.test(baseApiUrl)) {
+    throw new Error('Invalid prosody-peertube-uri')
+  }
+  if (!baseApiUrl) {
+    baseApiUrl = options.peertubeHelpers.config.getWebserverUrl()
+  }
+  baseApiUrl += getBaseRouterRoute(options) + 'api/'
+
   const authApiUrl = baseApiUrl + 'user' // FIXME: should be protected by apikey, but mod_auth_http cant handle params
   const roomApiUrl = baseApiUrl + 'room?apikey=' + apikey + '&jid={room.jid|jid_node}'
   const testApiUrl = baseApiUrl + 'test?apikey=' + apikey
@@ -118,7 +125,8 @@ async function getProsodyConfig (options: RegisterServerOptions): Promise<Prosod
   return {
     content,
     paths,
-    port
+    port,
+    baseApiUrl
   }
 }
 
diff --git a/server/lib/settings.ts b/server/lib/settings.ts
index d4ed53fc..26dbe209 100644
--- a/server/lib/settings.ts
+++ b/server/lib/settings.ts
@@ -103,6 +103,18 @@ Change it if this port is already in use on your server.<br>
 You can close this port on your firewall, it will not be accessed from the outer world.`
   })
 
+  registerSetting({
+    name: 'prosody-peertube-uri',
+    label: 'Peertube url for API calls',
+    type: 'input',
+    default: '',
+    private: true,
+    descriptionHTML:
+`Please let this settings empty if you don't know what you are doing.<br>
+In some rare case, Prosody can't call Peertube's API from its public URI.
+You can use this field to customise Peertube's URI for Prosody modules (for example with «http://localhost:9000»).`
+  })
+
   registerSetting({
     name: 'chat-server',
     label: 'XMPP service server',