Error when saving non-signup nodes: Call to undefined function _signup_node_completed()

I am trying to update a bunch of content_profile profile nodes in an update_N hook. Signup is installed on my site for my event nodes not enabled on the profile nodes.

However when I run the update, it errors with "Call to undefined function _signup_node_completed()" in node_form.inc on line 74. It seems weird that this function is being called as the node I am saving is not related to signup whatsoever.

Here is the block of code causing issue, at the end of the signup_save_node function called by signup_nodeapi:

$node = node_load($node->nid);
  if ( _signup_node_completed($node) && !empty($node->signup_status)) {
    // If this is an time-based node, and it's already past the close in
    // advance time (e.g. someone just changed the node start time), and
    // signups are still open, close them now.
    signup_close_signup($node->nid);
    drupal_set_message(t('%node_type start time is already past the signup close-in-advance time, signups now closed.', array('%node_type' => node_get_types('name', $node->type))));
  }

Looks like the operands are on the wrong sides of the && operator, the !empty($node->signup_status) should be checked before _signup_node_completed($node) but I am wondering whether logic should actually be placed in hook_nodeapi to ensure this function only gets run on signup-enabled nodes.