diff --git a/ui/jquery.ui.tabs.js b/ui/jquery.ui.tabs.js
index 0d920c3a137..8f09230c532 100644
--- a/ui/jquery.ui.tabs.js
+++ b/ui/jquery.ui.tabs.js
@@ -23,7 +23,12 @@ function getNextTabId() {
 
 function isLocal( anchor ) {
 	return anchor.hash.length > 1 &&
-		anchor.href.replace( rhash, "" ) === location.href.replace( rhash, "" );
+		anchor.href.replace( rhash, "" ) ===
+			location.href.replace( rhash, "" )
+				// support: Safari 5.1
+				// Safari 5.1 doesn't encode spaces in window.location
+				// but it does encode spaces from anchors (#8777)
+				.replace( /\s/g, "%20" );
 }
 
 $.widget( "ui.tabs", {