diff --git a/angular-flexslider.coffee b/angular-flexslider.coffee
index d668c01..96c47cf 100644
--- a/angular-flexslider.coffee
+++ b/angular-flexslider.coffee
@@ -68,7 +68,7 @@ angular.module('angular-flexslider', [])
 						if (toAdd.length == 1 and toRemove.length == 0) or toAdd.length == 0
 							# Remove items
 							for e in toRemove
-								e = removeSlide e, collection.indexOf(e)
+								e = removeSlide e, oldCollection.indexOf(e)
 								slider.removeSlide e.element if e
 							# Add items
 							for e in toAdd
diff --git a/angular-flexslider.js b/angular-flexslider.js
index f5932f7..47ebf4f 100644
--- a/angular-flexslider.js
+++ b/angular-flexslider.js
@@ -100,7 +100,7 @@
                 if ((toAdd.length === 1 && toRemove.length === 0) || toAdd.length === 0) {
                   for (_j = 0, _len1 = toRemove.length; _j < _len1; _j++) {
                     e = toRemove[_j];
-                    e = removeSlide(e, collection.indexOf(e));
+                    e = removeSlide(e, oldCollection.indexOf(e));
                     if (e) {
                       slider.removeSlide(e.element);
                     }