Rejected RepositoryMergeCheck for commit message needs page reload

I am rejecting a merge request if the commit message does not begin with “DTS”.

The problem is when the message is updated in the same window and the Merge button is pressed, I get a message saying “You are attempting to modify a pull request based on out-of-date information.”

Is there a way to reject a merge request without updating the object so that I am able to use the same window to update the commit message instead of reloading the page?

This is the gist of the function:

public class MergeDTSChecker implements RepositoryMergeCheck {
    public RepositoryHookResult preUpdate(@Nonnull PreRepositoryHookContext context,
                                          @Nonnull PullRequestMergeHookRequest request) {
        if (! message_matcher.matches()) {
            return RepositoryHookResult.rejected(summaryMsg, detailedMsg);
        } else {
            return RepositoryHookResult.accepted();

Thanks for your help.