diff --git a/Set.js b/Set.js
index b2451d2..6d62c25 100644
--- a/Set.js
+++ b/Set.js
@@ -13,7 +13,7 @@
 /*********************************************************************/
 
 // Set set operation shorthands...
-Set.prototype.unite = function(other){ 
+Set.prototype.unite = function(other=[]){ 
 	return new Set([...this, ...other]) }
 Set.prototype.intersect = function(other){
 	var test = other.has ?  
@@ -22,14 +22,14 @@ Set.prototype.intersect = function(other){
 	return new Set([...this]
 		.filter(function(e){ 
 			return other[test](e) })) }
-Set.prototype.subtract = function(other){
+Set.prototype.subtract = function(other=[]){
 	other = new Set(other)
 	return new Set([...this]
 		.filter(function(e){ 
 			return !other.has(e) })) }
 
 
-Map.prototype.sort = function(keys){
+Map.prototype.sort = function(keys=[]){
 	keys = (typeof(keys) == 'function' 
 			|| keys === undefined) ?
 		[...this].sort(keys)
diff --git a/package.json b/package.json
index e541490..ee039a0 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ig-types",
-  "version": "3.7.12",
+  "version": "3.7.13",
   "description": "Generic JavaScript types and type extensions...",
   "main": "main.js",
   "scripts": {