This happens for at least `Image.magickload_buffer` method, and IIRC some others as well. This happens due to this line: https://github.com/naqvis/crystal-vips/blob/1c40bc01dc31e8d40a4fc745f7ae0b47898299fa/src/vips/introspect.cr#L90 It's due to the missing enum member: ```c VIPS_ARGUMENT_NON_HASHABLE = 256 ``` https://github.com/libvips/libvips/blob/7258df0c4b5e9056ea24055121a2e620dfb1b3a1/libvips/include/vips/object.h#L76