Tinyint(byte),SmallInt(Int16) not compatible with Enum in EF5

Well if anyone is interested the problem is in enum's default type:

public enum MyEnumType 
{ One, Two, Three, All }

Since enum defaults to type int, [Underlying Type:{Byte}] doesn't match type of [External Type] {MyEnumType:Int} so to fix it for my original tinyint field you need to define your enum like this:

public enum MyEnumType : byte
{ One, Two, Three, All }