Explicit Constructor constructs the objects but doesn't pass correct values

public class Area
{
   [ExplicitConstructor]
   public Area(int areaId)
   {
       AreaId = areaId;
   }
   public int AreaId {get;}
}

with sql resultset equivalent to:
{ INT AreaId = 7 }

and dapper code:

await reader.ReadAsync < Area >();

passes zero as the constructor parameter. It should pass 7

Strangely enough the eventual value is actually correct even though there is no setter on the property but because the value passed into the constructor is wrong I can't do parameter validation on it which is the reason for the constructor in the first place.

Reproduce the reported Area example with the ReadAsync() entry point and a result containing AreaId = 7. Trace the explicit-constructor mapping path to determine why zero is passed, then verify that the constructor receives 7 while the resulting property remains correct.