libgen error

loading library from lib.yml
loading h2o definition from lib.yml
Unhandled exception: Bug: missing struct name (Exception)
  from CrystalLib::TypeMapper#map_internal<CrystalLib::StructOrUnion>:Crystal::Path
  from CrystalLib::PrefixImporter::import<Array(CrystalLib::ASTNode+), CrystalLib::PrefixMatcher>:Crystal::ASTNode+
  from LibGenerator::Generator#generate:Hash(String, String | Nil)
  from LibGenerator::run:Nil
  from main