Single_cat_title() print the title before text

When I use single_cat_title() get the name of the current category in archive page, it works perfectly but it prints the category title before the text

<h2>
    <?php 
        if (is_category()){
            echo 'Category: ' . single_cat_title();
        }
    ?>
</h2>

It says:

UncategorizedCategory:

How do I fix it? Thank you.