diff --git a/Documentation/NuttXCCodingStandard.html b/Documentation/NuttXCCodingStandard.html
index 27d5473746f..3924e3ab064 100644
--- a/Documentation/NuttXCCodingStandard.html
+++ b/Documentation/NuttXCCodingStandard.html
@@ -2765,6 +2765,10 @@ error:
       There is currently no requirement to conform any specific C++ version.
       However, for portability reasons, conformance to older, pre-C++11 standards is encouraged where reasonable.
     </p>
+  <li>
+    <p>
+      C++ file name extensions:  The extension <code>.cxx</code> is used for C++ source files; the extension <code>.hxx</code> is used for C++ header files.
+    </p>
   <li>
     <p>
       All naming must use <i>CamelCase</i>.