SignInManager.CreateUserPrincipalAsync() выдаёт NullReference

Пытаюсь вызвать signInManager.CreateUserPrincipalAsync(user), а он чудит:

Жалуется на NullReference, но где именно? Параметр не null и это видно на скрине.

Полный стректрейс:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Internal.ConcurrencyDetector.EnterCriticalSectionAsync(CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext(CancellationToken cancellationToken)
   at System.Linq.AsyncEnumerable.Aggregate_[TSource,TAccumulate,TResult](IAsyncEnumerable`1 source, TAccumulate seed, Func`3 accumulator, Func`2 resultSelector, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserStore`9.GetClaimsAsync(TUser user, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Identity.UserManager`1.GetClaimsAsync(TUser user)
   at Microsoft.AspNetCore.Identity.UserClaimsPrincipalFactory`1.GenerateClaimsAsync(TUser user)
   at Microsoft.AspNetCore.Identity.UserClaimsPrincipalFactory`2.GenerateClaimsAsync(TUser user)
   at Microsoft.AspNetCore.Identity.UserClaimsPrincipalFactory`1.CreateAsync(TUser user)
   at Microsoft.AspNetCore.Identity.SignInManager`1.CreateUserPrincipalAsync(TUser user)
   at NameThatTitle.WebApp.Controllers.AccountController.GetIdentity(String login, String password) in C:\Users\kamil\source\repos\NameThatTitle\src\NameThatTitle.WebApp\Controllers\AccountController.cs:line 129