diff --git a/src/experimental/tools/DummyMediaElement/mse.ts b/src/experimental/tools/DummyMediaElement/mse.ts
index fb8315a227..3e33499166 100644
--- a/src/experimental/tools/DummyMediaElement/mse.ts
+++ b/src/experimental/tools/DummyMediaElement/mse.ts
@@ -501,7 +501,7 @@ export class DummySourceBuffer
         this._lastKeyId = keyId;
 
         const completeChunks: Uint8Array[] =
-          otherChunks === null ? [] : extractCompleteChunks(otherChunks)[0] ?? [];
+          otherChunks === null ? [] : (extractCompleteChunks(otherChunks)[0] ?? []);
         const chunks: Uint8Array[] =
           initSegment === null ? completeChunks : [initSegment, ...completeChunks];