doc update: fix links
diff --git a/documentation/pyserial_api.rst b/documentation/pyserial_api.rst
index 4d7f3ba..5464b64 100644
--- a/documentation/pyserial_api.rst
+++ b/documentation/pyserial_api.rst
@@ -694,8 +694,8 @@
.. class:: rfc2217.Serial
- This implements a :rfc:`2217` compatible client. Port names are URLs_ in the
- form: ``rfc2217://<host>:<port>[?<option>[&<option>]]``
+ This implements a :rfc:`2217` compatible client. Port names are :ref:`URL
+ <URLs>` in the form: ``rfc2217://<host>:<port>[?<option>[&<option>]]``
This class API is compatible to :class:`Serial` with a few exceptions: