diff --git a/core/modules/widgets/checkbox.js b/core/modules/widgets/checkbox.js
index e2df3185c..fc987d815 100644
--- a/core/modules/widgets/checkbox.js
+++ b/core/modules/widgets/checkbox.js
@@ -116,7 +116,7 @@ CheckboxWidget.prototype.getValue = function() {
 				} else {
 					list = $tw.utils.parseStringArray(this.checkboxDefault || "") || [];
 				}
-			} else if (this.checkboxListIndex) {
+			} else if(this.checkboxListIndex) {
 				list = $tw.utils.parseStringArray(this.wiki.extractTiddlerDataItem(tiddler,this.checkboxListIndex,this.checkboxDefault || "")) || [];
 			} else {
 				list = this.wiki.filterTiddlers(this.checkboxFilter,this) || [];
@@ -215,6 +215,8 @@ CheckboxWidget.prototype.handleChangeEvent = function(event) {
 		if($tw.utils.isArray(fieldContents)) {
 			// Make a copy so we can modify it without changing original that's refrenced elsewhere
 			listContents = fieldContents.slice(0);
+		} else if(fieldContents === undefined) {
+			listContents = [];
 		} else if(typeof fieldContents === "string") {
 			listContents = $tw.utils.parseStringArray(fieldContents);
 			// No need to copy since parseStringArray returns a fresh array, not refrenced elsewhere