>>> URL.fromText(u"http://[3fff::1]/foo").asURI().asText() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/home/hawkowl/venvs/commands/lib/python2.7/site-packages/hyperlink/_url.py", line 1338, in to_uri new_host = self.host if not self.host else idna_encode(self.host, uts46=True).decode("ascii") File "/home/hawkowl/venvs/commands/lib/python2.7/site-packages/idna/core.py", line 340, in encode s = uts46_remap(s, std3_rules, transitional) File "/home/hawkowl/venvs/commands/lib/python2.7/site-packages/idna/core.py", line 332, in uts46_remap _unot(code_point), pos + 1, repr(domain))) idna.core.InvalidCodepoint: Codepoint U+003A not allowed at position 5 in u'3fff::1'