diff --git a/lib/marked.js b/lib/marked.js
index fc2afad0f9..5579eb09fa 100644
--- a/lib/marked.js
+++ b/lib/marked.js
@@ -32,7 +32,7 @@ var block = {
     + ')',
   def: /^ {0,3}\[(label)\]: *\n? *<?([^\s>]+)>?(?:(?: +\n? *| *\n *)(title))? *(?:\n+|$)/,
   table: noop,
-  lheading: /^([^\n]+)\n {0,3}(=|-){2,} *(?:\n+|$)/,  
+  lheading: /^([^\n]+)\n {0,3}(=|-){2,} *(?:\n+|$)/,
   paragraph: /^([^\n]+(?:\n(?!hr|heading|lheading| {0,3}>|<\/?(?:tag)(?: +|\n|\/?>)|<(?:script|pre|style|!--))[^\n]+)*)/,
   text: /^[^\n]+/
 };
diff --git a/package.json b/package.json
index 576ecb2c40..faeb155b62 100644
--- a/package.json
+++ b/package.json
@@ -31,7 +31,7 @@
   "devDependencies": {
     "@markedjs/html-differ": "^2.0.1",
     "cheerio": "^1.0.0-rc.3",
-    "commonmark": "^0.29.0",
+    "commonmark": "0.x",
     "eslint": "^5.16.0",
     "eslint-config-standard": "^12.0.0",
     "eslint-plugin-import": "^2.17.2",