diff --git a/extensions/voice-call/src/providers/stt-openai-realtime.test.ts b/extensions/voice-call/src/providers/stt-openai-realtime.test.ts
index f7170d3bc14..fa2bdb54c07 100644
--- a/extensions/voice-call/src/providers/stt-openai-realtime.test.ts
+++ b/extensions/voice-call/src/providers/stt-openai-realtime.test.ts
@@ -2,18 +2,18 @@ import { describe, expect, it } from "vitest";
 import type { RealtimeSTTConfig } from "./stt-openai-realtime.js";
 import { OpenAIRealtimeSTTProvider } from "./stt-openai-realtime.js";
 
-type ProviderInternals = OpenAIRealtimeSTTProvider & {
+type ProviderInternals = {
   vadThreshold: number;
   silenceDurationMs: number;
 };
 
-function createProvider(config: RealtimeSTTConfig): ProviderInternals {
-  return new OpenAIRealtimeSTTProvider(config) as ProviderInternals;
+function readProviderInternals(config: RealtimeSTTConfig): ProviderInternals {
+  return new OpenAIRealtimeSTTProvider(config) as unknown as ProviderInternals;
 }
 
 describe("OpenAIRealtimeSTTProvider constructor defaults", () => {
   it("uses vadThreshold: 0 when explicitly configured (max sensitivity)", () => {
-    const provider = createProvider({
+    const provider = readProviderInternals({
       apiKey: "sk-test", // pragma: allowlist secret
       vadThreshold: 0,
     });
@@ -21,7 +21,7 @@ describe("OpenAIRealtimeSTTProvider constructor defaults", () => {
   });
 
   it("uses silenceDurationMs: 0 when explicitly configured", () => {
-    const provider = createProvider({
+    const provider = readProviderInternals({
       apiKey: "sk-test", // pragma: allowlist secret
       silenceDurationMs: 0,
     });
@@ -29,7 +29,7 @@ describe("OpenAIRealtimeSTTProvider constructor defaults", () => {
   });
 
   it("falls back to defaults when values are undefined", () => {
-    const provider = createProvider({
+    const provider = readProviderInternals({
       apiKey: "sk-test", // pragma: allowlist secret
     });
     expect(provider.vadThreshold).toBe(0.5);