         async.series([
             # add account_id to the project's set of users (for the given group)
             (cb) =>
-                query = "UPDATE projects SET #{opts.group}=#{opts.group}+{?} WHERE project_id=?"
-                @cql(query, [opts.account_id, opts.project_id], cb)
+                query = "UPDATE projects SET #{opts.group}=#{opts.group}+{#{opts.account_id}} WHERE project_id=?"
+                @cql(query, [opts.project_id], cb)
             # add project_id to the set of projects (for the given group) for the user's account
             (cb) =>
-                query = "UPDATE accounts SET #{opts.group}=#{opts.group}+{?} WHERE account_id=?"
-                @cql(query, [opts.project_id, opts.account_id], cb)
+                query = "UPDATE accounts SET #{opts.group}=#{opts.group}+{#{opts.project_id}} WHERE account_id=?"
+                @cql(query, [opts.account_id], cb)
         ], opts.cb)
 
     remove_user_from_project: (opts) =>

                ttl = "USING ttl #{opts.ttl}"
            else
                ttl = ""
            query = "UPDATE account_creation_actions #{ttl} SET actions=actions+{?} WHERE email_address=?"
            @cql(query, [misc.to_json(opts.action), opts.email_address], opts.cb)
        else
            @select
                table     : 'account_creation_actions'

            table : required
            delta : 1
            cb    : required
        query = "UPDATE counts SET count=count+? where table_name=?"
        @cql query, [new cql.types.Long(opts.delta), opts.table], opts.cb

    # Get count of entries in a table for which we manually maintain the count.
    get_table_counter: (opts) =>
