2 files changed, 2 insertions, 1 deletions
diff --git a/history.txt b/history.txt
index da0aebf..fd4acc8 100755
--- a/history.txt
+++ b/history.txt
@@ -2155,3 +2155,4 @@ ______
 * Objects: stop replacing the empty string with the number zero in watchers
 * Threads: initialize new variables with zero (instead of null)
 * Objects: fixed #465
+* Threads: fixed #457
diff --git a/objects.js b/objects.js
index 41f3e4a..5de468b 100644
--- a/objects.js
+++ b/objects.js
@@ -4144,7 +4144,7 @@ StageMorph.prototype.init = function (globals) {
     this.keysPressed = {}; // for handling keyboard events, do not persist
     this.blocksCache = {}; // not to be serialized (!)
     this.paletteCache = {}; // not to be serialized (!)
-    this.lastAnswer = null; // last user input, do not persist
+    this.lastAnswer = ''; // last user input, do not persist
     this.activeSounds = []; // do not persist
 
     this.trailsCanvas = null;