diff --git a/Kobo-Integration.md b/Kobo-Integration.md
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--- a/Kobo-Integration.md
+++ b/Kobo-Integration.md
@@ -7,7 +7,8 @@ I'd recommend waiting a little bit for this cautionary message do disappear if y
 
 ## Setup
 As prerequiste you need to install the dependencies listed in optional-requirements.txt in the Kobo integration section. 
-Kobo integration must first be enabled in Calibre-Web by toggling ON the **Enable Kobo sync** checkbox in the **Basic configuration >> Feature Configuration** page.
+Kobo integration must first be enabled in Calibre-Web by toggling ON the **Enable Kobo sync** checkbox in the **Basic configuration >> Feature Configuration** page. 
+If you are accessing your Calibre-Web instance from your Kobo via some sort of portforwarding mechanism (e.g. your router maps port X to machine Y on port Z), please change the **External Port** setting to port Y in this example (the external port). This necessary due to a bug in HTTP-requests the Kobo reader creates and can't be avoided.
 
 The **Kobo eReader.conf** file found under the **.kobo/Kobo** directory on Kobo devices is used to configure which URL the device uses for syncing books. By default, the config file contains the following row: