diff --git a/src/Gui/OnlineDocumentation.cpp b/src/Gui/OnlineDocumentation.cpp
index c1d4648e23..165873ff3e 100644
--- a/src/Gui/OnlineDocumentation.cpp
+++ b/src/Gui/OnlineDocumentation.cpp
@@ -143,8 +143,8 @@ QByteArray PythonOnlineHelp::loadResource(const QString& filename) const
             "'#ffffff', '#7799ee')\n"
             "def bltinlink(name):\n"
             "    return '<a href=\"%s.html\">%s</a>' % (name, name)\n"
-            "names = filter(lambda x: x != '__main__',\n"
-            "               sys.builtin_module_names)\n"
+            "names = list(filter(lambda x: x != '__main__',\n"
+            "               sys.builtin_module_names))\n"
             "contents = pydoc.html.multicolumn(names, bltinlink)\n"
             "indices = ['<p>' + pydoc.html.bigsection(\n"
             "    'Built-in Modules', '#ffffff', '#ee77aa', contents)]\n"