diff --git a/index.js b/index.js
index e8fe1b8..1bbc058 100644
--- a/index.js
+++ b/index.js
@@ -53,7 +53,7 @@ function hook(base, m, filename) {
 }
 
 function compile(base, code, filename) {
-  var sourcemap = convertSourceMap.fromMapFileSource(code, '.').toObject();
+  var sourcemap = convertSourceMap.fromSource(code).toObject();
   code = convertSourceMap.removeMapFileComments(code);
 
   var babelOutput = babel.transform(code, getBabelOpts(filename, sourcemap));