diff --git a/apps/web/src/app/api/__tests__/realtime-session-route.test.ts b/apps/web/src/app/api/__tests__/realtime-session-route.test.ts
index ca69a73d6..e723fe739 100644
--- a/apps/web/src/app/api/__tests__/realtime-session-route.test.ts
+++ b/apps/web/src/app/api/__tests__/realtime-session-route.test.ts
@@ -4,7 +4,7 @@ import { GET, POST } from '@/app/api/realtime/session/route';
 const ORIGINAL_OPENAI_KEY = process.env.OPENAI_API_KEY;
 const ORIGINAL_SAFETY_IDENTIFIER = process.env.OPENAI_SAFETY_IDENTIFIER;
 
-function sdpRequest(body: string) {
+function sdpRequest(body: string): Request {
   return new Request('http://localhost/api/realtime/session', {
     method: 'POST',
     headers: { 'content-type': 'application/sdp' },
@@ -12,7 +12,11 @@ function sdpRequest(body: string) {
   });
 }
 
-function upstreamResponse(body: unknown, status = 200, headers: HeadersInit = { 'content-type': 'application/json' }) {
+function upstreamResponse(
+  body: unknown,
+  status = 200,
+  headers: HeadersInit = { 'content-type': 'application/json' },
+): Response {
   return new Response(typeof body === 'string' ? body : JSON.stringify(body), {
     status,
     headers,
diff --git a/apps/web/src/app/api/realtime/session/route.ts b/apps/web/src/app/api/realtime/session/route.ts
index ab2277c4c..65b9e3250 100644
--- a/apps/web/src/app/api/realtime/session/route.ts
+++ b/apps/web/src/app/api/realtime/session/route.ts
@@ -85,7 +85,7 @@ function upstreamUnreachable(
   return Response.json({ error, code }, { status: 502 });
 }
 
-function getOpenAiHeaders(contentType?: string) {
+function getOpenAiHeaders(contentType?: string): Record<string, string> | null {
   const apiKey = process.env.OPENAI_API_KEY;
 
   if (!apiKey) {