subscription updater store proxy returns undefined instead of record proxy

I have the following subscription:

```
const subscription = graphql`
subscription EventSubscription($id: ID!) {
eventChildrenUpdate(id: $id) {
guestEntries {
id
name
}
}
}
`;
```

And create a subscription with an updater:

```
requestSubscription(
relayEnvironment,
{
subscription,
variables: { id: entityId },
updater: store => {
console.log({event: store.get(entityId)});
}
}
);
```

The relay chrome debugger clearly shows that the record with entityId exists in the store, and the same updater function works with mutations, but for some reason the subscription updater returns undefined for that record.

Any ideas why this might be happening and any way to fix or work around this?