diff --git a/lib/credentials/coreAuthHelpers.ts b/lib/credentials/coreAuthHelpers.ts
index 5fec4da..1f31898 100644
--- a/lib/credentials/coreAuthHelpers.ts
+++ b/lib/credentials/coreAuthHelpers.ts
@@ -2,7 +2,7 @@ import { AccessToken } from "@azure/core-auth";
 
 interface TokenResponseLike {
   accessToken: string;
-  expiresOn: Date | string;
+  expiresOn?: Date | string;
 }
 
 /**
@@ -16,12 +16,19 @@ export function prepareToken<T extends TokenResponseLike>(
   scopes: string | string[] | undefined): T | AccessToken {
   // Scopes will contain _some_ value if a parameter was passed to getToken
   if (scopes !== undefined) {
-    return {
-      token: token.accessToken,
-      expiresOnTimestamp:
+    // Start with a default 'expiresOn' and then replace with
+    // the actual 'expiresOn' if one is given
+    let expiresOnTimestamp: number = Date.now() + 60 * 60 * 1000;
+    if (token.expiresOn) {
+      expiresOnTimestamp =
         typeof token.expiresOn === "string"
           ? Date.parse(token.expiresOn)
-          : token.expiresOn.getTime()
+          : token.expiresOn.getTime();
+    }
+
+    return {
+      token: token.accessToken,
+      expiresOnTimestamp
     } as AccessToken;
   } else {
     return token;
diff --git a/lib/credentials/tokenClientCredentials.ts b/lib/credentials/tokenClientCredentials.ts
index 405730b..11b57b0 100644
--- a/lib/credentials/tokenClientCredentials.ts
+++ b/lib/credentials/tokenClientCredentials.ts
@@ -6,7 +6,6 @@ import { ServiceClientCredentials } from "@azure/ms-rest-js";
 export interface TokenResponse {
   readonly tokenType: string;
   readonly accessToken: string;
-  readonly expiresOn: Date;
   readonly [x: string]: any;
 }
 
diff --git a/test/credentials/coreAuthHelpersTests.ts b/test/credentials/coreAuthHelpersTests.ts
index 3c168b9..85f30e0 100644
--- a/test/credentials/coreAuthHelpersTests.ts
+++ b/test/credentials/coreAuthHelpersTests.ts
@@ -3,6 +3,7 @@
 
 import { assert } from "chai";
 import { prepareToken } from "../../lib/credentials/coreAuthHelpers";
+import { AccessToken } from "@azure/core-auth";
 
 describe("prepareToken", function() {
   it("returns an AccessToken when scope is set", function() {
@@ -31,6 +32,14 @@ describe("prepareToken", function() {
     });
   });
 
+  it("returns an AccessToken with expiresOnTimestamp when expiresOn is empty", function() {
+    const result = prepareToken({
+      accessToken: "token",
+    }, "scope") as AccessToken;
+
+    assert.isNumber(result.expiresOnTimestamp);
+  });
+
   it("returns an unmodified TokenResponse when scope is not set", function() {
     const expiresOn = new Date();
     const tokenResponse = {