hashmap.ipldsch fails to parse

hashmap fixtures fails to parse:

https://github.com/ipld/js-ipld-schema/blob/master/test/fixtures/hashmap/hashmap.ipldsch

Error parsing schema @ line:34 col:18: Expected "#", "advanced", "type", [ \t\n\r], or end of input but "[" found

I am not sure if this is a bug in the hashmap schema or js-ipld-schema