diff --git a/index.d.ts b/index.d.ts
index 50ef56e0..c93b5a99 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -196,6 +196,9 @@ declare module 'bedrock-protocol' {
     // tokens to join the backend server. Cached after the first login.
     // If this is not specified, the client will be disconnected with a login prompt.
     onMsaCode?(data: ServerDeviceCodeResponse, client: Client): any
+    // prismarine-auth configuration
+    flow?: string,
+    deviceType?: string
   }
 
   export class Relay extends Server {
diff --git a/src/relay.js b/src/relay.js
index 86784576..3128a7d6 100644
--- a/src/relay.js
+++ b/src/relay.js
@@ -186,6 +186,8 @@ class Relay extends Server {
   async openUpstreamConnection (ds, clientAddr) {
     const options = {
       authTitle: this.options.authTitle,
+      flow: this.options.flow,
+      deviceType: this.options.deviceType,
       offline: this.options.destination.offline ?? this.options.offline,
       username: this.options.offline ? ds.profile.name : ds.profile.xuid,
       version: this.options.version,