GUACAMOLE-514: Add missing parameter tag.
diff --git a/src/protocols/vnc/auth.h b/src/protocols/vnc/auth.h
index e978aa9..155a48d 100644
--- a/src/protocols/vnc/auth.h
+++ b/src/protocols/vnc/auth.h
@@ -47,6 +47,10 @@
* The rfbClient associated with the VNC connection requiring the
* authentication.
*
+ * @param credentialType
+ * The credential type being requested, as defined by the libVNCclient
+ * code in the rfbclient.h header.
+ *
* @return
* The rfbCredential object that contains the required credentials.
*/