Index: src/wp-admin/js/theme.js
===================================================================
--- src/wp-admin/js/theme.js	(revision 26206)
+++ src/wp-admin/js/theme.js	(working copy)
@@ -682,11 +682,14 @@
 		// Render results
 		this.view.render();
 
-		// Calls the routes functionality
-		this.routes();
+		if ( window.history && window.history.pushState ) {
 
-		// Set ups history with pushState and our root
-		Backbone.history.start({ root: themes.data.settings.root });
+			// Calls the routes functionality
+			this.routes();
+
+			// Set ups history with pushState and our root
+			Backbone.history.start({ root: themes.data.settings.root, pushState: true });
+		}
 	},
 
 	routes: function() {