diff --git a/history.txt b/history.txt
index 57aafd1d..774f798e 100755
--- a/history.txt
+++ b/history.txt
@@ -2176,7 +2176,6 @@ ______
 ------
 * Blocks: add “ringify” to every context menu that already has “unringify”
 
-
 140708
 ------
 * Threads: show error messages for custom blocks (propagating to the script’s top block)
@@ -2211,3 +2210,7 @@ ______
 * GUI: Use new mechanism for unique costume names on the paint editor, renamed costumes and costumes dragged and dropped onto sprite icons
 * add “letter” option to the split block’s list of delimiters, Thanks, Michael!
 * update German translation
+
+140721
+------
+* fixed #518
diff --git a/threads.js b/threads.js
index 469fb7f1..9251b95a 100644
--- a/threads.js
+++ b/threads.js
@@ -83,7 +83,7 @@ ArgLabelMorph, localize, XML_Element, hex_sha512*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.threads = '2014-July-18';
+modules.threads = '2014-July-21';
 
 var ThreadManager;
 var Process;
@@ -2871,7 +2871,8 @@ Context.prototype.continuation = function () {
 Context.prototype.copyForContinuation = function () {
     var cpy = copy(this),
         cur = cpy,
-        isReporter = !(this.expression instanceof Array);
+        isReporter = !(this.expression instanceof Array ||
+            isString(this.expression));
     if (isReporter) {
         cur.prepareContinuationForBinding();
         while (cur.parentContext) {
@@ -2886,7 +2887,8 @@ Context.prototype.copyForContinuation = function () {
 Context.prototype.copyForContinuationCall = function () {
     var cpy = copy(this),
         cur = cpy,
-        isReporter = !(this.expression instanceof Array);
+        isReporter = !(this.expression instanceof Array ||
+            isString(this.expression));
     if (isReporter) {
         this.expression = this.expression.fullCopy();
         this.inputs = [];