Adding a property to Grid Datasource doesn't add a Column to existing values

I have created a GRID Datasource with 5 properties and have added 1 row of values for each. When I am trying add an additional property , it doesn't add a column to the existing Configuration. 

 

The only workaround is I have change the type from Grid to something else and come back to Grid , but then that wipes out all the data stored. 

 

Looks like this is a bug Or Am I doing something wrong here ?