diff --git a/acorn.js b/acorn.js
index 6323b1fc6a..81abc2da38 100644
--- a/acorn.js
+++ b/acorn.js
@@ -444,7 +444,8 @@
       ++tokPos;
       ch = input.charCodeAt(tokPos);
     }
-    (tokComments || (tokComments = [])).push(input.slice(start, tokPos));
+    if (options.trackComments)
+      (tokComments || (tokComments = [])).push(input.slice(start, tokPos));
   }
 
   // Called at the start of the parse and after every token. Skips
@@ -878,7 +879,8 @@
       if (tokCommentsAfter) {
         node.commentsAfter = tokCommentsAfter;
         tokCommentsAfter = null;
-      } else if (lastFinishedNode && lastFinishedNode.end === lastEnd) {
+      } else if (lastFinishedNode && lastFinishedNode.end === lastEnd &&
+                 lastFinishedNode.commentsAfter) {
         node.commentsAfter = lastFinishedNode.commentsAfter;
         lastFinishedNode.commentsAfter = null;
       }
diff --git a/index.html b/index.html
index 216adce76a..033605112c 100644
--- a/index.html
+++ b/index.html
@@ -263,7 +263,8 @@ the right position.</p>             </td>             <td class="code">
       <span class="o">++</span><span class="nx">tokPos</span><span class="p">;</span>
       <span class="nx">ch</span> <span class="o">=</span> <span class="nx">input</span><span class="p">.</span><span class="nx">charCodeAt</span><span class="p">(</span><span class="nx">tokPos</span><span class="p">);</span>
     <span class="p">}</span>
-    <span class="p">(</span><span class="nx">tokComments</span> <span class="o">||</span> <span class="p">(</span><span class="nx">tokComments</span> <span class="o">=</span> <span class="p">[])).</span><span class="nx">push</span><span class="p">(</span><span class="nx">input</span><span class="p">.</span><span class="nx">slice</span><span class="p">(</span><span class="nx">start</span><span class="p">,</span> <span class="nx">tokPos</span><span class="p">));</span>
+    <span class="k">if</span> <span class="p">(</span><span class="nx">options</span><span class="p">.</span><span class="nx">trackComments</span><span class="p">)</span>
+      <span class="p">(</span><span class="nx">tokComments</span> <span class="o">||</span> <span class="p">(</span><span class="nx">tokComments</span> <span class="o">=</span> <span class="p">[])).</span><span class="nx">push</span><span class="p">(</span><span class="nx">input</span><span class="p">.</span><span class="nx">slice</span><span class="p">(</span><span class="nx">start</span><span class="p">,</span> <span class="nx">tokPos</span><span class="p">));</span>
   <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-53">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-53">&#182;</a>               </div>               <p>Called at the start of the parse and after every token. Skips
 whitespace and comments, and, if <code>options.trackComments</code> is on,
 will store all skipped comments in <code>tokComments</code>.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">function</span> <span class="nx">skipSpace</span><span class="p">()</span> <span class="p">{</span>
@@ -605,7 +606,8 @@ operator node, not the second literal node.</p>             </td>             <t
       <span class="k">if</span> <span class="p">(</span><span class="nx">tokCommentsAfter</span><span class="p">)</span> <span class="p">{</span>
         <span class="nx">node</span><span class="p">.</span><span class="nx">commentsAfter</span> <span class="o">=</span> <span class="nx">tokCommentsAfter</span><span class="p">;</span>
         <span class="nx">tokCommentsAfter</span> <span class="o">=</span> <span class="kc">null</span><span class="p">;</span>
-      <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="nx">lastFinishedNode</span> <span class="o">&amp;&amp;</span> <span class="nx">lastFinishedNode</span><span class="p">.</span><span class="nx">end</span> <span class="o">===</span> <span class="nx">lastEnd</span><span class="p">)</span> <span class="p">{</span>
+      <span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="nx">lastFinishedNode</span> <span class="o">&amp;&amp;</span> <span class="nx">lastFinishedNode</span><span class="p">.</span><span class="nx">end</span> <span class="o">===</span> <span class="nx">lastEnd</span> <span class="o">&amp;&amp;</span>
+                 <span class="nx">lastFinishedNode</span><span class="p">.</span><span class="nx">commentsAfter</span><span class="p">)</span> <span class="p">{</span>
         <span class="nx">node</span><span class="p">.</span><span class="nx">commentsAfter</span> <span class="o">=</span> <span class="nx">lastFinishedNode</span><span class="p">.</span><span class="nx">commentsAfter</span><span class="p">;</span>
         <span class="nx">lastFinishedNode</span><span class="p">.</span><span class="nx">commentsAfter</span> <span class="o">=</span> <span class="kc">null</span><span class="p">;</span>
       <span class="p">}</span>