EF retrieves incorrect decimal precision

In Entity Framework Core you can do:

[Column(TypeName = "decimal(19,4)")]
public decimal MyDecimal { get; set; }

Turns out I needed to specify the precision the same way, but in the fluent mapping for ClassA. Specifying it in OnModelCreating() didn't do it, but in the fluent mapping did. Specifically:

Property(u => u.MyDecimal).HasPrecision(19, 4);