Sql exception when removing item from Scope.ScopeClaims

[hrjjml]

here's my code snippet:

scope.ScopeClaims.Remove(claim);
_scopeContext.Update(scope);
await _scopeContext.SaveChangesAsync();

here's the exception:
System.Data.SqlClient.SqlException: Cannot insert the value NULL into column 'ScopeId', table 'ScopeClaims'; column does not allow nulls. UPDATE fails.
The statement has been terminated.