[Plugin: Woocommerce] if is_shop or is_cart not working

I am trying to modify the head and foot of my woocommerce pages. I have an if statement that is supposed to target the shop and cart of woocommerce but it isn’t. If I modify the php after the is statement nothing changes. But if I modify the php in the else statement is works:

This doesn’t work:

<?php if (function_exists('woocommerce')): ?>
		<?php if (is_cart() || is_shop()): ?>
			<?php get_template_part('inc/CHANGE'); ?>
		<?php endif ?>
	<?php else: ?>
		<?php get_template_part('inc/page-header'); ?>
	<?php endif ?>

This does work:

<?php if (function_exists('woocommerce')): ?>
		<?php if (is_cart() || is_shop()): ?>
			<?php get_template_part('inc/page-header'); ?>
		<?php endif ?>
	<?php else: ?>
		<?php get_template_part('inc/CHANGE'); ?>
	<?php endif ?>

I think the function woocommerce might not be properly defined, because this also works:

<?php if (is_cart() || is_shop()): ?>
        <?php get_template_part('inc/header-shop'); ?>
    <?php else: ?>
        <?php get_template_part('inc/page-header'); ?>
    <?php endif ?>