post-thumbnail is not a valid thumbnail size

[oncletom]

If I refer to the documentation or the source code, if I pass no argument to the_post_thumbnail, we are supposed to have a thumbnail.

However, I always get the full size picture (which is pretty bad).

the_post_thumbnail('post-thumbnail') gives the full size.
the_post_thumbnail() gives the full size.
the_post_thumbnail('thumbnail') gives the thumbnail size.

I guess there is a problem there. The default value should be thumbnail and not post-thumbnail.

[scribu]

From the docs of the_post_thumbnail():

 * @param int $size Optional. Image size.  Defaults to 'post-thumbnail', which theme sets using set_post_thumbnail_size( $width, $height, $crop_flag );.