diff --git a/tools/node.js b/tools/node.js
index 7bba3231..29d5632d 100644
--- a/tools/node.js
+++ b/tools/node.js
@@ -73,13 +73,13 @@ exports.minify = function(files, options) {
     } else {
         if (typeof files == "string")
             files = [ files ];
-        files.forEach(function(file){
+        files.forEach(function(file, i){
             var code = options.fromString
                 ? file
                 : fs.readFileSync(file, "utf8");
             sourcesContent[file] = code;
             toplevel = UglifyJS.parse(code, {
-                filename: options.fromString ? "?" : file,
+                filename: options.fromString ? i : file,
                 toplevel: toplevel
             });
         });