diff --git a/README.md b/README.md
index f05aadd..a8e0bb3 100644
--- a/README.md
+++ b/README.md
@@ -893,10 +893,15 @@ require('ig-types/Set')
 Replace value in set with other value retaining item order
 ```bnf
 <set>.replace(<old>, <new>)
-    -> <union-set>
+    -> <set>
 ```
 
-Note that this might not be cheap for very large sets.
+This might not be cheap for very large sets, to simply replace 
+the value without sorting use:
+```bnf
+<set>.replace(<old>, <new>, false)
+    -> <set>
+```
 
 
 ### `<set>.unite(..)`
diff --git a/Set.js b/Set.js
index cd7fa84..bb2c7af 100644
--- a/Set.js
+++ b/Set.js
@@ -46,16 +46,20 @@ object.Mixin('SetMixin', 'soft', {
 					add(e) } }.bind(this))
 		return this },
 
-	replace: function(old, value){
+	replace: function(old, value, ordered=true){
 		// nothing to do...
 		if(!this.has(old) || old === value){
 			return this }
-		var order = [...this]
-		// XXX is this fast enough???
-		order[order.lastIndexOf(old)] = value
+		if(ordered){
+			var order = [...this]
+			// XXX is this fast enough???
+			order[order.lastIndexOf(old)] = value }
+
 		this.delete(old)
 		this.add(value)
-		this.sort(order)
+
+		ordered
+			&& this.sort(order)
 		return this },
 })
 
diff --git a/package.json b/package.json
index 09eecbf..52ff28e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ig-types",
-  "version": "6.5.0",
+  "version": "6.5.1",
   "description": "Generic JavaScript types and type extensions...",
   "main": "main.js",
   "scripts": {