Getting "Schema must contain uniquely named types but contains multiple types named" for a single type

Hello, I have the following schema:

@ObjectType()
class Action {
  @Field(type => Skill, { nullable: true })
  skill?: Skill;
}

@ObjectType()
export class ActionResult {
  @Field(type => [Action])
  actions!: Action[];
  @Field({ nullable: true })
  count?: number
}

@ObjectType()
export class Skill {}

@Resolver(Action)
export class ActionResolver  extends BaseResolver {
  @Query(returns => ActionResult)
  async actions (@Args() args: ActionArgs, @Info() info){

  }

  @FieldResolver()
  async skill(@Root() action: Action) {
  }
}

@Resolver(Skill)
export class SkillResolver extends BaseResolver {
  @Query(returns => [Skill])
  async allSkills (){

  }
}

From this I generate a schema like this:

  return buildSchema({
    resolvers: [ActionResolver, SkillResolver],
    emitSchemaFile: { path: 'schema.graphql' },
  })

And I get the error:

UnhandledPromiseRejectionWarning: Error: Schema must contain uniquely named types but contains multiple types named "Skill".