diff --git a/js/ui/iconGrid.js b/js/ui/iconGrid.js
index b93f6c018..f893d5d27 100644
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -305,7 +305,7 @@ const IconGrid = new Lang.Class({
     _onStyleChanged: function() {
         let themeNode = this.actor.get_theme_node();
         this._spacing = themeNode.get_length('spacing');
-        this._item_size = themeNode.get_length('-shell-grid-item-size');
+        this._item_size = themeNode.get_length('-shell-grid-item-size') || ICON_SIZE;
         this._grid.queue_relayout();
     },