diff --git a/index.bs b/index.bs
index 3a46a6a..6a13a3c 100644
--- a/index.bs
+++ b/index.bs
@@ -330,7 +330,7 @@ dictionary RTCEncodedVideoFrameMetadata {
     unsigned long temporalIndex;
     unsigned long synchronizationSource;
     octet payloadType;
-  sequence<unsigned long> contributingSources;
+    sequence<unsigned long> contributingSources;
 };
 </pre>