diff --git a/lib/index.js b/lib/index.js
index 6b301e8..db4b9ec 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -488,6 +488,7 @@ MarkdownIt.prototype.use = function (plugin /*, params, ... */) {
  * and then pass updated object to renderer.
  **/
 MarkdownIt.prototype.parse = function (src, env) {
+  env = (env) ? env : {}
   var state = new this.core.State(src, this, env);
 
   this.core.process(state);