diff --git a/js/lite/src/connection/connect.ts b/js/lite/src/connection/connect.ts
index f03f4f14f..15e6ea41e 100644
--- a/js/lite/src/connection/connect.ts
+++ b/js/lite/src/connection/connect.ts
@@ -74,7 +74,7 @@ export async function connect(url: URL, props?: ConnectProps): Promise<Establish
 	const stream = await Stream.open(session);
 
 	// @ts-expect-error - TODO: add protocol to WebTransport
-	const protocol = session instanceof WebTransport ? session.protocol : undefined;
+	const protocol: string | undefined = session instanceof WebTransport ? session.protocol : undefined;
 
 	// Choose setup encoding based on negotiated WebTransport protocol (if any).
 	let setupVersion: Ietf.Version;
@@ -82,7 +82,7 @@ export async function connect(url: URL, props?: ConnectProps): Promise<Establish
 		setupVersion = Ietf.Version.DRAFT_16;
 	} else if (protocol === Ietf.ALPN.DRAFT_15) {
 		setupVersion = Ietf.Version.DRAFT_15;
-	} else if (protocol === undefined) {
+	} else if (protocol === "" || protocol === undefined) {
 		setupVersion = Ietf.Version.DRAFT_14;
 	} else {
 		throw new Error(`unsupported WebTransport protocol: ${protocol}`);
diff --git a/js/lite/src/ietf/connection.ts b/js/lite/src/ietf/connection.ts
index d382effff..c447ac965 100644
--- a/js/lite/src/ietf/connection.ts
+++ b/js/lite/src/ietf/connection.ts
@@ -288,6 +288,7 @@ export class Connection implements Established {
 					stream.stop(new Error("cancel"));
 				})
 				.catch((err: unknown) => {
+					console.error("error processing object stream", err);
 					stream.stop(err);
 				});
 		}
@@ -297,13 +298,9 @@ export class Connection implements Established {
 	 * Handles a single object stream.
 	 */
 	async #runObjectStream(stream: Reader) {
-		try {
-			// we don't support other stream types yet
-			const header = await Group.decode(stream);
-			await this.#subscriber.handleGroup(header, stream);
-		} catch (err) {
-			console.error("error processing object stream", err);
-		}
+		// we don't support other stream types yet
+		const header = await Group.decode(stream);
+		await this.#subscriber.handleGroup(header, stream);
 	}
 
 	/**
diff --git a/js/lite/src/ietf/object.ts b/js/lite/src/ietf/object.ts
index 21619b38e..abe7284db 100644
--- a/js/lite/src/ietf/object.ts
+++ b/js/lite/src/ietf/object.ts
@@ -137,7 +137,7 @@ export class Frame {
 	static async decode(r: Reader, flags: GroupFlags): Promise<Frame> {
 		const delta = await r.u53();
 		if (delta !== 0) {
-			console.warn(`object ID delta is not supported, ignoring: ${delta}`);
+			throw new Error(`object ID delta is not supported: ${delta}`);
 		}
 
 		if (flags.hasExtensions) {
diff --git a/js/lite/src/ietf/subscriber.ts b/js/lite/src/ietf/subscriber.ts
index 73577d89e..db64345db 100644
--- a/js/lite/src/ietf/subscriber.ts
+++ b/js/lite/src/ietf/subscriber.ts
@@ -287,7 +287,7 @@ export class Subscriber {
 		const producer = new Group(group.groupId);
 
 		if (group.subGroupId !== 0) {
-			console.warn("subgroup ID is not supported, ignoring");
+			throw new Error("subgroups are not supported");
 		}
 
 		try {
diff --git a/rs/moq-lite/src/ietf/subscriber.rs b/rs/moq-lite/src/ietf/subscriber.rs
index c9ea159cd..f6ab97484 100644
--- a/rs/moq-lite/src/ietf/subscriber.rs
+++ b/rs/moq-lite/src/ietf/subscriber.rs
@@ -358,7 +358,8 @@ impl<S: web_transport_trait::Session> Subscriber<S> {
 		tracing::trace!(?group, "received group header");
 
 		if group.sub_group_id != 0 {
-			tracing::warn!(sub_group_id = %group.sub_group_id, "subgroup ID is not supported, stripping");
+			tracing::warn!(sub_group_id = %group.sub_group_id, "subgroup ID is not supported, dropping stream");
+			return Err(Error::Unsupported);
 		}
 
 		let producer = {
@@ -409,7 +410,8 @@ impl<S: web_transport_trait::Session> Subscriber<S> {
 	) -> Result<(), Error> {
 		while let Some(id_delta) = stream.decode_maybe::<u64>().await? {
 			if id_delta != 0 {
-				tracing::warn!(id_delta = %id_delta, "object ID gaps not supported, ignoring");
+				tracing::warn!(id_delta = %id_delta, "object ID delta is not supported, dropping stream");
+				return Err(Error::Unsupported);
 			}
 
 			if group.flags.has_extensions {