Call to undefined function imageapi_image_overlay()

Recieving following error:
Fatal error: Call to undefined function imageapi_image_overlay() in /var/www/html/sites/all/modules/imagecache_actions/canvasactions.inc on line 451

Using:
ImageCache 6.x-2.0-beta10
Imagecache Canvas Actions 6.x-2.x-dev
ImageAPI 6.x-1.8
ImageAPI GD2 6.x-1.8
ImageAPI ImageMagick Disabled

Actions:
Scale 130x100%
Underlay (background) xpos:0 , ypos:0 alpha:100%. file path: gal_background_001.jpg, dimensions:original

Underlay settings:
X offset: 0
Y offset: 0
opacity: 100
file name: gal_background_001.jpg
final dimensions: original (dimensions are retained)

Function exists in module, not sure why it isn't available to canvasactions.inc.

imagecache_actions\imageapi_image_overlay.inc(35):

function imageapi_image_overlay(&$image, &$layer, $x, $y, $alpha = 100, $reverse = FALSE) {
if (is_string($layer) ) {
if (! file_exists($layer)) {
trigger_error("Image file does not exist. Attempted to overlay $layer", E_USER_ERROR);
return FALSE;
}
$layer = imageapi_image_open($layer);
}
// else $layer had better be an image handle

$x = imagecache_actions_keyword_filter($x, $image->info['width'], $layer->info['width']);
$y = imagecache_actions_keyword_filter($y, $image->info['height'], $layer->info['height']);

return imageapi_toolkit_invoke('overlay', $image, array($layer, $x, $y, $alpha, $reverse));
}

Will troubleshoot this weekend if not sooner.