diff --git a/bin/js_features.js b/bin/js_features.js
index 178492fc..95a0c7cf 100755
--- a/bin/js_features.js
+++ b/bin/js_features.js
@@ -80,12 +80,12 @@ function processFile(file, print_ast, features, json_formatting, skip_minified)
 	try {
 		var output = UglifyJS.extractFeatures(code, file, print_ast, features, skip_minified);
 	} catch (ex){
-		if (ex instanceof UglifyJS.JS_Parse_Error){
-			sys.error("ERROR: ".red + "cannot parse file '" + file + "'");
-		} else if (ex instanceof  UglifyJS.JS_Minified_Error){
+		if (ex instanceof UglifyJS.Parse_Error){
+			sys.error("ERROR: ".red + "cannot parse file '" + file + "': " + ex.message);
+		} else if (ex instanceof  UglifyJS.Minified_Error){
 			//sys.error("WARN: ".yellow + "skipping minified file '" + file + "'");
 		} else {
-			sys.error("ERROR: ".red + "'" + file + "'" + ex);
+			sys.error("ERROR: ".red + "'" + file + "': " + ex);
 		}
 
 		return;
diff --git a/lib/feature_extractor.js b/lib/feature_extractor.js
index a181fc33..4aa2467f 100644
--- a/lib/feature_extractor.js
+++ b/lib/feature_extractor.js
@@ -58,14 +58,22 @@ function replaceMangled(code, file) {
 	return stream.toString();
 }
 
-function JS_Minified_Error(message) {
+function Minified_Error(message) {
 	this.message = message;
 }
 
+function Parse_Error(ex) {
+	this.message = ex.toString();
+}
+
 function extractFeatures(code, file, print_ast, features, skip_minified) {
 	var toplevel;
 
-	toplevel = parseFile(code, file);
+	try {
+		toplevel = parseFile(code, file);
+	} catch (ex){
+		throw new Parse_Error(ex);
+	}
 
 	extendAst(toplevel);
 
@@ -74,7 +82,7 @@ function extractFeatures(code, file, print_ast, features, skip_minified) {
 	}
 
 	if (skip_minified && isMinified(toplevel, code, file)){
-		throw new JS_Minified_Error("Skipping minified file");
+		throw new Minified_Error("Skipping minified file");
 		//console.warn("Skipping minified file: '%s'", file);
 		//return null;
 	}
@@ -82,7 +90,7 @@ function extractFeatures(code, file, print_ast, features, skip_minified) {
 	var feature_outputter = new FeatureJsonOutputter();
 	feature_outputter.openElem();
 	feature_outputter.openArray("query");
-	
+
 	if (features.indexOf("ASTREL") != -1) {
 		generateAstFeatures(toplevel, feature_outputter);
 	}
@@ -104,8 +112,8 @@ function extractFeatures(code, file, print_ast, features, skip_minified) {
 
 /* -----[ functions ]----- */
 
-function nodeToString(node) {
-	if (node == null) return null;		
+function nodeToString(node, parent) {
+	if (node == null) return null;
 
 	if (node instanceof AST_Symbol){
 		if (node instanceof AST_This ){
@@ -120,31 +128,37 @@ function nodeToString(node) {
 		return GIVEN + "!" + nodeType(node) + "!" + String(node.value).slice(0,64);
 	} else if (node instanceof AST_Sub){
 		//x[1], x -> expression, 1 -> property
-		return nodeToString(node.expression) + "[]";
+		return (nodeToString(node.expression, node) != null) ? nodeToString(node.expression, node) + "[]" : null;
 	} else if (node instanceof AST_PropAccess){
 		return GIVEN + node.property;
 	} else if (node instanceof AST_Defun) {
 		//function foo(...) { ... }		
-		return nodeToString(node.name);
+		return nodeToString(node.name, node);
 	} else if (node instanceof AST_VarDef){
 		// var x = function () { ... }
-		return nodeToString(node.name);
+		return nodeToString(node.name, node);
 	} else if (node instanceof AST_Assign){
 		//x = function () { ... }
-		return nodeToString(node.left);
+		return nodeToString(node.left, node);
 	} else if (node instanceof AST_ObjectProperty){
 		// { "x" : function () { ... } }
 		return GIVEN + node.key;	
 	} else if (node instanceof AST_Call){
 		//x.foo( function () { ... } )
 		//foo( function () { ... } )
-		return nodeToString(node.expression);		
+		return nodeToString(node.expression,  node);
 	} else if (node instanceof AST_Lambda) {
 		if (node.parent instanceof AST_Call){
 			//'node.parent.expression != node' as lambda can call itself
-			return (node.parent.expression == node) ? null : nodeToString(node.parent.expression) + "(" + node.child_id + ")";
-		} 
-		return nodeToString(node.parent);
+			if (node.parent.expression == node) {
+				return null;
+			}
+
+			return (nodeToString(node.parent.expression, node) != null) ? nodeToString(node.parent.expression, node)  + "(" + node.child_id + ")" : null;
+		}
+		if (node.parent != parent) {
+			return nodeToString(node.parent, node);
+		}
 	}
 
 	return null;
@@ -543,8 +557,10 @@ StringMap.prototype.getId = function(input){
 
 /* ------------------------ */
 
-function escapeString(input){	
-	return encodeURIComponent(input);
+function escapeString(input){
+	//escape method escapes certain characters that encodeURIComponent cannot process
+	//unescape is used to make the resulting string smaller
+	return unescape(encodeURIComponent(escape(input)));
 }
 
 function parseFile(code, file) {	
diff --git a/lib/parse.js b/lib/parse.js
index 35ce7ef2..1486e763 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -196,7 +196,7 @@ function JS_Parse_Error(message, line, col, pos) {
 };
 
 JS_Parse_Error.prototype.toString = function() {
-    return this.message + " (line: " + this.line + ", col: " + this.col + ", pos: " + this.pos + ")" + "\n\n" + this.stack;
+    return this.message + " (line: " + this.line + ", col: " + this.col + ", pos: " + this.pos + ")";// + "\n\n" + this.stack;
 };
 
 function js_error(message, filename, line, col, pos) {