Internal error when creating AddressBook

[WhyNotHugo]

When I try to create an AddressBook, I get an "internal error", and nothing is logged. Here's my request:

curl \
    -u user1: \
    -X POST http://localhost:8080/jmap/ \
    -H "Content-Type: application/json; charset=utf8" \
    -d '{"using":["urn:ietf:params:jmap:core","urn:ietf:params:jmap:contacts"],"methodCalls":[["AddressBook/set",{"create":{"new0":{"name":"Blah"}}},"0"]]}'

Response:

{
  "methodResponses": [
    [
      "AddressBook/set",
      {
        "oldState": "21",
        "newState": "21",
        "created": null,
        "updated": null,
        "destroyed": null,
        "notCreated": {
          "new0": {
            "type": "serverFail",
            "description": "Internal Error"
          }
        },
        "notUpdated": null,
        "notDestroyed": null,
        "accountId": "user1"
      },
      "0"
    ]
  ],
  "sessionState": "0"
}

An almost-identical query to create a calendar works fine:

curl \
    -u user1: \
    -X POST http://localhost:8080/jmap/ \
    -H "Content-Type: application/json; charset=utf8" \
    -d '{"using":["urn:ietf:params:jmap:core","urn:ietf:params:jmap:calendars"],"methodCalls":[["Calendar/set",{"create":{"new0":{"name":"Blah"}}},"0"]]}'