diff --git a/src/auth/awsclient.ts b/src/auth/awsclient.ts
index 561954bb..5a06c7f7 100644
--- a/src/auth/awsclient.ts
+++ b/src/auth/awsclient.ts
@@ -356,21 +356,19 @@ export class AwsClient extends BaseExternalAccountClient {
     return process.env['AWS_REGION'] || process.env['AWS_DEFAULT_REGION'];
   }
 
-  private get securityCredentialsFromEnvironment():
-    | AwsSecurityCredentialsFromEnvironment
-    | undefined {
-    let awsSecurityCredentials;
-    // Check if both AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are available.
+  private get securityCredentialsFromEnv(): AwsSecurityCredentials | null {
+    // Both AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are required.
     if (
       process.env['AWS_ACCESS_KEY_ID'] &&
       process.env['AWS_SECRET_ACCESS_KEY']
     ) {
-      awsSecurityCredentials = {
+      return {
         accessKeyId: process.env['AWS_ACCESS_KEY_ID'],
         secretAccessKey: process.env['AWS_SECRET_ACCESS_KEY'],
         token: process.env['AWS_SESSION_TOKEN'],
       };
     }
-    return awsSecurityCredentials;
+
+    return null;
   }
 }