GraphQL: Cart query merchandise returns empty object

[F24s]

Cart query merchandise returns empty object:

merchandise {
  ... on ProductVariant {
    id
    title
  }
}

 
It returns an object when I have the same query on for example the cartLinesAdd mutation.
But when querying the cart by ID, it doesn't seem to work...

[F24s · Accepted solution]

Found it, this caused the issue:

addTypename: false