diff --git a/core/language/en-GB/Misc.multids b/core/language/en-GB/Misc.multids
index 0718b08b8..0890424a5 100644
--- a/core/language/en-GB/Misc.multids
+++ b/core/language/en-GB/Misc.multids
@@ -7,7 +7,7 @@ ConfirmCancelTiddler: Do you wish to discard changes to the tiddler "<$text text
 ConfirmDeleteTiddler: Do you wish to delete the tiddler "<$text text=<<title>>/>"?
 ConfirmOverwriteTiddler: Do you wish to overwrite the tiddler "<$text text=<<title>>/>"?
 ConfirmEditShadowTiddler: You are about to edit a ShadowTiddler. Any changes will override the default system making future upgrades non-trivial. Are you sure you want to edit "<$text text=<<title>>/>"?
-InvalidFieldName: Illegal characters in field name "<$text text=<<fieldName>>/>". Fields can only contain lowercase letters and the characters underscore (`_`), hyphen (`-`) and period (`.`)
+InvalidFieldName: Illegal characters in field name "<$text text=<<fieldName>>/>". Fields can only contain lowercase letters, digits and the characters underscore (`_`), hyphen (`-`) and period (`.`)
 MissingTiddler/Hint: Missing tiddler "<$text text=<<currentTiddler>>/>" - click {{$:/core/images/edit-button}} to create
 RecentChanges/DateFormat: DDth MMM YYYY
 RelativeDate/Future/Days: <<period>> days from now
diff --git a/core/modules/utils/utils.js b/core/modules/utils/utils.js
index 5a01fd387..0ed21f88c 100644
--- a/core/modules/utils/utils.js
+++ b/core/modules/utils/utils.js
@@ -413,6 +413,18 @@ exports.parseTextReference = function(textRef) {
 	}
 };
 
+/*
+Checks whether a string is a valid fieldname
+*/
+exports.isValidFieldName = function(name) {
+	if(!name || typeof name !== "string") {
+		return false;
+	}
+	name = name.toLowerCase().trim();
+	var fieldValidatorRegEx = /^[a-z0-9\-\._]+$/mg;
+	return fieldValidatorRegEx.test(name);
+};
+
 /*
 Extract the version number from the meta tag or from the boot file
 */
diff --git a/core/modules/widgets/fieldmangler.js b/core/modules/widgets/fieldmangler.js
index d902e755a..afb60b577 100644
--- a/core/modules/widgets/fieldmangler.js
+++ b/core/modules/widgets/fieldmangler.js
@@ -71,12 +71,11 @@ FieldManglerWidget.prototype.handleRemoveFieldEvent = function(event) {
 };
 
 FieldManglerWidget.prototype.handleAddFieldEvent = function(event) {
-	var tiddler = this.wiki.getTiddler(this.mangleTitle),
-		fieldValidatorRegEx = /^[a-z\-\._]+$/mg;
+	var tiddler = this.wiki.getTiddler(this.mangleTitle);
 	if(tiddler && typeof event.param === "string") {
 		var name = event.param.toLowerCase().trim();
 		if(name !== "" && !$tw.utils.hop(tiddler.fields,name)) {
-			if(!fieldValidatorRegEx.test(name)) {
+			if(!$tw.utils.isValidFieldName(name)) {
 				alert($tw.language.getString(
 					"InvalidFieldName",
 					{variables: