diff --git a/src/adapt/viewer.js b/src/adapt/viewer.js
index <HASH>..<HASH> 100644
--- a/src/adapt/viewer.js
+++ b/src/adapt/viewer.js
@@ -615,7 +615,7 @@ adapt.viewer.Viewer.prototype.sizeIsGood = function() {
  * @param {number} pageIndex
  */
 adapt.viewer.Viewer.prototype.setPageSize = function(pageSize, pageSheetSize, spineIndex, pageIndex) {
-    this.pageSizes.push(pageSize);
+    this.pageSizes[pageIndex] = pageSize;
     this.setPageSizePageRules(pageSheetSize, spineIndex, pageIndex);
 };
 /**
page size should be added to pageSizes by index.

setPageSize() can be called multiple times for a same page.