diff --git a/README.md b/README.md
index 4175d07..4df26f3 100644
--- a/README.md
+++ b/README.md
@@ -2150,7 +2150,7 @@ Introspection
 ```python
 <bool> = hasattr(<object>, '<attr_name>')  # Checks if getattr() raises an error.
 value  = getattr(<object>, '<attr_name>')  # Raises AttributeError if attribute is missing.
-setattr(<object>, '<attr_name>', value)    # Only works on user-defined classes.
+setattr(<object>, '<attr_name>', value)    # Only works on classes with __dict__ attribute.
 delattr(<object>, '<attr_name>')           # Equivalent to `del <object>.<attr_name>`.
 ```
 
diff --git a/index.html b/index.html
index 8210fa2..c229165 100644
--- a/index.html
+++ b/index.html
@@ -1882,7 +1882,7 @@ last_el          = op.methodcaller(<span class="hljs-string">'pop'</span>)(&lt;l
 
 <pre><code class="python language-python hljs">&lt;bool&gt; = hasattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)  <span class="hljs-comment"># Checks if getattr() raises an error.</span>
 value  = getattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)  <span class="hljs-comment"># Raises AttributeError if attribute is missing.</span>
-setattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>, value)    <span class="hljs-comment"># Only works on user-defined classes.</span>
+setattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>, value)    <span class="hljs-comment"># Only works on classes with __dict__ attribute.</span>
 delattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)           <span class="hljs-comment"># Equivalent to `del &lt;object&gt;.&lt;attr_name&gt;`.</span>
 </code></pre>
 <div><h3 id="parameters-1">Parameters</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> inspect <span class="hljs-keyword">import</span> signature