Angular - Error: 10 $digest() iterations reached. Aborting

i'm trying to put a random integer in my ng-src path, like that:

  <img ng-src="{{randomPicture()}}" alt="">

And here's my basic function in my controller:

$scope.randomPicture = function(){
  var PATH = 'assets/images/';
  var image = Math.floor((Math.random() * 12) + 1);
  var ext = '.jpg';
  var randomPic = PATH + image + ext;

  return randomPic;
};

The images are displayed but in the console i have this error:

Error: [$rootScope:infdig] 10 $digest() iterations reached. Aborting!

I found many questions on that here in stackoverflow but i still can't get rid of that error. Thanks for your help.