diff --git a/acorn.js b/acorn.js
index 76d10903e9..e7d8c44d3d 100644
--- a/acorn.js
+++ b/acorn.js
@@ -101,7 +101,7 @@
 
   function setOptions(opts) {
     options = opts || {};
-    for (var opt in defaultOptions) if (!options.hasOwnProperty(opt))
+    for (var opt in defaultOptions) if (!Object.prototype.hasOwnProperty.call(options, opt))
       options[opt] = defaultOptions[opt];
     sourceFile = options.sourceFile || null;
   }
diff --git a/index.html b/index.html
index b92bc1327f..045d0fb29b 100644
--- a/index.html
+++ b/index.html
@@ -65,7 +65,7 @@ file in every node's <code>loc</code> object.</p>             </td>
 
   <span class="kd">function</span> <span class="nx">setOptions</span><span class="p">(</span><span class="nx">opts</span><span class="p">)</span> <span class="p">{</span>
     <span class="nx">options</span> <span class="o">=</span> <span class="nx">opts</span> <span class="o">||</span> <span class="p">{};</span>
-    <span class="k">for</span> <span class="p">(</span><span class="kd">var</span> <span class="nx">opt</span> <span class="k">in</span> <span class="nx">defaultOptions</span><span class="p">)</span> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nx">options</span><span class="p">.</span><span class="nx">hasOwnProperty</span><span class="p">(</span><span class="nx">opt</span><span class="p">))</span>
+    <span class="k">for</span> <span class="p">(</span><span class="kd">var</span> <span class="nx">opt</span> <span class="k">in</span> <span class="nx">defaultOptions</span><span class="p">)</span> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nb">Object</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">hasOwnProperty</span><span class="p">.</span><span class="nx">call</span><span class="p">(</span><span class="nx">options</span><span class="p">,</span> <span class="nx">opt</span><span class="p">))</span>
       <span class="nx">options</span><span class="p">[</span><span class="nx">opt</span><span class="p">]</span> <span class="o">=</span> <span class="nx">defaultOptions</span><span class="p">[</span><span class="nx">opt</span><span class="p">];</span>
     <span class="nx">sourceFile</span> <span class="o">=</span> <span class="nx">options</span><span class="p">.</span><span class="nx">sourceFile</span> <span class="o">||</span> <span class="kc">null</span><span class="p">;</span>
   <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-13">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-13">&#182;</a>               </div>               <p>The <code>getLineInfo</code> function is mostly useful when the