Photoshop :: Display Flickers When Going Back In History Using A Script?

I noticed that the display flickers when going back in history using a script (I'm using Javascript), like so :
 
var docRef = app.activeDocument;
docRef.activeHistoryState = docRef.historyStates[docRef.historyStates.length-2];
 
What precisely happens is the document briefly turns to a checker (the same checker that indicates transparency).
 
It also happens when using "executeAction" with the action recorded by the ScriptListener.But, it only happens when the function is called from within a script, not when I'm using the history panel.
 
This is a problem because it makes it a lot harder to see what changed between the two history states.i'm using CS6.