Aspect switcher warning

warning: imagecopyresampled() expects parameter 5 to be long, string given in .../sites/all/modules/imageapi/imageapi_gd.module on line 98.

This warning appears when using the aspect switcher action and one of the presets, landscape preset or portrait preset, contains a crop action with any of its offsets parameter set as special keyword (left, center or right). For example:

mini_100w preset:
Scale -- 100x100%
Crop -- width: 100, height: 80, xoffset: center, yoffset: center

mini_80h preset:
Scale -- 100%x80
Crop -- width: 100, height: 80, xoffset: center, yoffset: center

switch preset:
Aspect Switch -- Portrait size: mini_100w. Landscape size: mini_80h

The presets containing the crop work fine with their offset configured with special keywords. But the preset with the aspect switch generates the warning. If crop offsets are configured with a numeric value, the warning is not appearing. That's why I think the problem is in aspect switch which for some reason is not interpreting the offsets when they have the special values.