https://github.com/graphql-python/graphene/blob/d46d8e8c33b1432ed664d94f432f357c44f3447e/graphene/types/field.py#L23 Because the first argument in the constructor is 'type', so a field named 'type' in 'extra_args' is not permitted: TypeError: __init__() got multiple values for argument 'type' Could by solved by renaming 'type' in the constructor to 'type_' (which is good python practice anyway for python builtins).