error when using linqkit's predicate with an expression method

Question

A little background:
I'm using a Linq provider (MsCrm2011 Linq provider, but doesn't really matter) that doesn't support certain operations.
Specifically, it doesn't support Contains() inside an expression.
Meaning- something like this will not work: var users = DataContext.Users.Where(user => userIds.Contains(user.Id)).

The solution I've found for it was to use LinqKit's predicate, so instead of userIds.Contains(...) I'll have user.Id == userIds[0] || user.Id == userIds[1] ... || user.Id == userIds[100].

To this end, I've defined the following function, which takes an arbitrary collection and arbitrary expression, and applies the 'Or' on them:

private IQueryable<TCrmEntity> FilterByCollection<TCrmEntity, T>(IQueryable<TCrmEntity> entities, IEnumerable<T> collection, Expression<Func<TCrmEntity, T, bool>> filterFunction)
    {
      var predicate = PredicateBuilder.False<TCrmEntity>();
      predicate = collection.Aggregate(predicate, (current, collectionElement) => current.Or(entity => filterFunction.Invoke(entity,collectionElement)));

      var query = entities.AsExpandable()
        .Where(predicate);

      return query;
    }

this way, I can use any kind of collection and any kind of expression.
For example, see this test run (using an in-memory users collection): var res = FilterByCollection(users.AsQueryable(), rolesList, (account, role) => account.Role == role) to find all users that have one of the given roles.

However, I'm getting the following exception when I'm running the above example- variable 'entity' of type 'User' referenced from scope '', but it is not defined.

Any ideas?

P.S. not sure how relevant this is, but when I'm actually using the Crm data context instead of an in-memory collection, I'm not getting this error. :/