Param-illegal error

I wanted to import P5192, which has the datatype wikibase-lexeme. This is the result of entity.get_json():
{'labels': {'en': {'language': 'en', 'value': 'Wikidata property example for lexemes'}, 'de': {'language': 'de', 'value': 'Wikidata-Eigenschaftsbeispiel für Lexeme'}}, 'descriptions': {'en': {'language': 'en', 'value': 'example where this Wikidata property is used; target lexeme is one that would use this property, with qualifier the property being described given the associated value'}}, 'aliases': {'en': [{'language': 'en', 'value': 'property example for lexemes'}]}, 'type': 'property', 'claims': {'P1': [{'mainsnak': {'snaktype': 'value', 'property': 'P1', 'datatype': 'external-id', 'datavalue': {'value': 'P5192', 'type': 'string'}}, 'type': 'statement', 'rank': 'normal', 'references': [{'snaks': {}, 'snaks-order': []}]}]}, 'datatype': 'wikibase-lexeme'}

However, I am getting the following error:
{'error': {'code': 'param-illegal', 'info': 'A datatype was expected, but either missing or not recognized.', 'messages': [{'name': 'wikibase-api-not-recognized-datatype', 'parameters': [], 'html': {'': 'A datatype was expected, but either missing or not recognized.'}}], '': 'See http://wikibase.svc/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/postorius/lists/mediawiki-api-announce.lists.wikimedia.org/> for notice of API deprecations and breaking changes.'}}

I am confused, why that would be, as wikibase-lexeme is a valid data type.