The Retail, Wholesale and Department Store Union (RWDSU) has formally filed objections with the National Labor Relations Board (NLRB) over Amazon’s conduct during the union drive at its Bessemer, Ala., facility.

The union, which would have represented the warehouse employees, alleged in a filing late Friday night that Amazon illegally interfered in the workers’ right to vote in a “fair and free election.”

Workers ended up rejecting the unionization by 1,798 to 738, according to a tally that has yet to be certified. A successful challenge could ultimately invalidate that result and trigger a second election.

“Working people deserve better than the way Amazon has conducted itself during this campaign,” RWDSU President Stuart Appelbaum said in a statement Monday. “We won’t rest until workers’ voices are heard fairly under the law. When they are, we believe they will be victorious in this historic and critical fight to unionize the first Amazon warehouse in the United States.”