diff --git a/lib/marked.js b/lib/marked.js
index f2fb9b6be7..c85f74ac95 100644
--- a/lib/marked.js
+++ b/lib/marked.js
@@ -1274,14 +1274,32 @@ Parser.prototype.tok = function() {
  */
 
 function escape(html, encode) {
-  return html
-    .replace(!encode ? /&(?!#?\w+;)/g : /&/g, '&')
-    .replace(/</g, '&lt;')
-    .replace(/>/g, '&gt;')
-    .replace(/"/g, '&quot;')
-    .replace(/'/g, '&#39;');
+  if (encode) {
+    if (escape.escapeTest.test(html)) {
+      return html.replace(escape.escapeReplace, function (ch) { return escape.replacements[ch] });
+    }
+  } else {
+    if (escape.escapeTestNoEncode.test(html)) {
+      return html.replace(escape.escapeReplaceNoEncode, function (ch) { return escape.replacements[ch] });
+    }
+  }
+
+  return html;
 }
 
+escape.escapeTest = /[&<>"']/;
+escape.escapeReplace = /[&<>"']/g;
+escape.replacements = {
+  '&': '&amp;',
+  '<': '&lt;',
+  '>': '&gt;',
+  '"': '&quot;',
+  "'": '&#39;'
+};
+
+escape.escapeTestNoEncode = /[<>"']|&(?!#?\w+;)/;
+escape.escapeReplaceNoEncode = /[<>"']|&(?!#?\w+;)/g;
+
 function unescape(html) {
   // explicitly match decimal, hex, and named HTML entities
   return html.replace(/&(#(?:\d+)|(?:#x[0-9A-Fa-f]+)|(?:\w+));?/ig, function(_, n) {