diff --git a/HISTORY.md b/HISTORY.md
index 853f5f3a..ef90a363 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -67,6 +67,9 @@
     * German
     * French
 
+### 2019-04-22
+* Threads: fixed variable binding for "arguments", turned dictionary key into a Symbol
+
 ### 2019-04-12
 * Objects: enabled text-variables as inputs for graphic effects / pen attributes
 * updated amination library with graphic effects and audio attributes
diff --git a/snap.html b/snap.html
index adabb420..8f4115b4 100755
--- a/snap.html
+++ b/snap.html
@@ -7,7 +7,7 @@
         <script type="text/javascript" src="src/morphic.js?version=2019-02-07"></script>
         <script type="text/javascript" src="src/widgets.js?version=2019-04-05"></script>
         <script type="text/javascript" src="src/blocks.js?version=2019-04-11"></script>
-        <script type="text/javascript" src="src/threads.js?version=2019-04-11"></script>
+        <script type="text/javascript" src="src/threads.js?version=2019-04-22"></script>
         <script type="text/javascript" src="src/objects.js?version=2019-04-12"></script>
         <script type="text/javascript" src="src/gui.js?version=2019-04-10"></script>
         <script type="text/javascript" src="src/paint.js?version=2019-02-22"></script>
diff --git a/src/threads.js b/src/threads.js
index 91ca1477..19df0b32 100644
--- a/src/threads.js
+++ b/src/threads.js
@@ -60,9 +60,9 @@ degrees, detect, nop, radians, ReporterSlotMorph, CSlotMorph, RingMorph, Sound,
 IDE_Morph, ArgLabelMorph, localize, XML_Element, hex_sha512, TableDialogMorph,
 StageMorph, SpriteMorph, StagePrompterMorph, Note, modules, isString, copy,
 isNil, WatcherMorph, List, ListWatcherMorph, alert, console, TableMorph, Color,
-TableFrameMorph, ColorSlotMorph, isSnapObject, Map, newCanvas*/
+TableFrameMorph, ColorSlotMorph, isSnapObject, Map, newCanvas, Symbol*/
 
-modules.threads = '2019-April-11';
+modules.threads = '2019-April-22';
 
 var ThreadManager;
 var Process;
@@ -1018,7 +1018,7 @@ Process.prototype.reify = function (topBlock, parameterNames, isCustomBlock) {
             context.expression.allEmptySlots().forEach(function (slot) {
                 i += 1;
                 if (slot instanceof MultiArgMorph) {
-                    slot.bindingID = ['arguments'];
+                    slot.bindingID = Symbol.for('arguments');
                 } else {
                     slot.bindingID = i;
                 }
@@ -1120,8 +1120,8 @@ Process.prototype.evaluate = function (
     // assign arguments to parameters
 
     // assign the actual arguments list to the special
-    // parameter ID ['arguments'], to be used for variadic inputs
-    outer.variables.addVar(['arguments'], args);
+    // parameter ID Symbol.for('arguments'), to be used for variadic inputs
+    outer.variables.addVar(Symbol.for('arguments'), args);
 
     // assign arguments that are actually passed
     if (parms.length > 0) {
@@ -1220,8 +1220,8 @@ Process.prototype.initializeFor = function (context, args) {
     // assign arguments to parameters
 
     // assign the actual arguments list to the special
-    // parameter ID ['arguments'], to be used for variadic inputs
-    outer.variables.addVar(['arguments'], args);
+    // parameter ID Symbol.for('arguments'), to be used for variadic inputs
+    outer.variables.addVar(Symbol.for('arguments'), args);
 
     // assign arguments that are actually passed
     if (parms.length > 0) {