diff --git a/api/README.runserver.txt b/api/README.runserver.txt
new file mode 100644
index 0000000000..7b04917f01
--- /dev/null
+++ b/api/README.runserver.txt
@@ -0,0 +1,11 @@
+== Installation on Ubuntu VM ==
+
+apt-get update
+apt-get install nodejs npm git build-essential
+npm install -g express html5 lru-cache jquery pegjs async jshashes
+adduser --system --home /var/lib/parsoid parsoid
+cd /var/lib/parsoid
+git clone
+https://gerrit.wikimedia.org/r/p/mediawiki/extensions/VisualEditor.git
+cd VisualEditor/api
+./runserver.sh
diff --git a/api/runserver.sh b/api/runserver.sh
new file mode 100755
index 0000000000..21826a6f00
--- /dev/null
+++ b/api/runserver.sh
@@ -0,0 +1,6 @@
+#!/bin/sh
+# redirect port 80 to unprivileged port 8000
+iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8000
+
+# run the server as non-privileged user
+nohup sudo -u nobody node server.js &
diff --git a/modules/parser/ext.core.LinkHandler.js b/modules/parser/ext.core.LinkHandler.js
index fa5f3f7404..2f4d43b67a 100644
--- a/modules/parser/ext.core.LinkHandler.js
+++ b/modules/parser/ext.core.LinkHandler.js
@@ -343,9 +343,13 @@ function ExternalLinkHandler( manager, isInclude ) {
 		// img_options production only.
 		ExternalLinkHandler.prototype.imageParser = new PegTokenizer();
 	}
-	this.onEnd();
+	this._reset();
 }
 
+ExternalLinkHandler.prototype._reset = function () {
+	this.linkCount = 1;
+};
+
 ExternalLinkHandler.prototype.rank = 1.15;
 ExternalLinkHandler.prototype._imageExtensions = {
 	'jpg': true,
@@ -403,6 +407,10 @@ ExternalLinkHandler.prototype.onExtLink = function ( token, manager, cb ) {
 	//console.warn('extlink href: ' + href );
 	//console.warn( 'content: ' + JSON.stringify( content, null, 2 ) );
 	// validate the href
+	if ( ! content.length ) {
+		content = ['[' + this.linkCount + ']'];
+		this.linkCount++;
+	}
 	if ( this.imageParser.tokenizeURL( href ) ) {
 		if ( content.length === 1 && 
 				content[0].constructor === String &&
@@ -433,10 +441,6 @@ ExternalLinkHandler.prototype.onExtLink = function ( token, manager, cb ) {
 				].concat( content, [ new EndTagTk( 'a' )])
 		} );
 	} else {
-		if ( content === '' ) {
-			content = ['[' + this.linkCount + ']'];
-			this.linkCount++;
-		}
 		cb( {
 			tokens: ['[', href, ' ' ].concat( content, [']'] )
 		} );
@@ -444,8 +448,8 @@ ExternalLinkHandler.prototype.onExtLink = function ( token, manager, cb ) {
 };
 
 ExternalLinkHandler.prototype.onEnd = function ( token, manager, cb ) {
-	this.linkCount = 1;
-	return { tokens: token };
+	this._reset();
+	cb( { tokens: [ token ] } );
 };
 
 
diff --git a/modules/parser/mediawiki.TokenTransformManager.js b/modules/parser/mediawiki.TokenTransformManager.js
index 66bafad9bf..0a792b1a6f 100644
--- a/modules/parser/mediawiki.TokenTransformManager.js
+++ b/modules/parser/mediawiki.TokenTransformManager.js
@@ -435,6 +435,12 @@ AsyncTokenTransformManager.prototype.transformTokens = function ( tokens, parent
 				// maybeSyncReturn callback
 				if ( resTokens && resTokens.length ) {
 					if ( resTokens.length === 1 ) {
+						if ( resTokens[0] === undefined ) {
+							console.warn('transformer ' + transformer + 
+									' returned undefined token!');
+							resTokens.shift();
+							break;
+						}
 						if ( token === resTokens[0] && ! resTokens.rank ) {
 							// token not modified, continue with
 							// transforms.