Unexpected T_ENDWHILE in loop.php

Hello,
I’m doing a new theme from scratch (the previous one hasn’t been updated for serveral years) and I wanted to try it.
Everything seemed to go well except when I want to list posts, I get this error :

Parse error: syntax error, unexpected T_ENDWHILE in /wp-content/themes/pro/loop.php on line 41

Here is the cleaned up code :

<?php if (have_posts()) : ?>
  <?php while (have_posts()) : the_post(); ?>
    <div class="panel panel-default">
        <div class="panel-heading">
            <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a><small>, le <?php the_date(); ?></small></h2>
        </div>
        <div class="panel-body">
            <?php
                if ( $post->post_excerpt ){
                    the_excerpt();?>
                    <div class="btn-group">
                        <button type="button" class="btn btn-default"><a href="<?php the_permalink(); ?>">Lire la suite <i class="fa fa-arrow-right fa-fw"></i></a></button>
                    </div>
                <?php }
                else {
                    the_content();?>
        </div>
        <div class="panel-footer">
            <div class="btn-group">
                <button type="button" class="btn btn-default"><a href="<?php the_permalink(); ?>#comments"><i class="fa fa-comments fa-fw"></i> <?php get_comments_number(); ?></a></button>
            </div>
             
            <i class="fa fa-folder-open fa-fw"></i> Catégories : <?php the_category(', ') ?>
        </div>
    </div>
  <?php endwhile; ?>
<?php else : ?>
    <div class="jumbotron">
        <h1>Il n'y a rien à afficher.</h1>
    </div>
<?php endif; ?>

I looked up at my previous themes and the while looks OK to me. What could cause this ?