Custom path to ImageMagick "convert" not being read correctly

I've created a custom content type with an Image field attached to it. When I save a piece of content of that type, I get an error "An image thumbnail was not able to be created.". Looking at the Drupal log, the message is "The specified ImageMagick path /usr/bin/convert does not exist". However, I've configured my ImageAPI module to point to /usr/local/bin/convert to find convert, and this is saved correctly according to the config screen.

Looking in the variables table in my database, the variable "imageapi_imagemagick_convert" is correctly set to "/usr/local/bin/convert", so it looks like the ImageMagick module is not correctly reading the variable in the database.

In a couple places in the module code, I see:

$convert_path = variable_get('imageapi_imagemagick_convert', '/usr/bin/convert');

So I'm guessing that somehow variable_get() is not returning the right value, and the default value is getting used instead. Could this be a Drupal bug, or maybe a module weight bug or what?