diff --git a/README.md b/README.md
index 4064df8..e2304a8 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ Alternatively you can donate cryptocurrencies:
 * Create or modify feed2toot.ini file in order to configure feed2toot:
 
         [mastodon]
+        instance_url=https://mastodon.social
         user_credentials=feed2toot_usercred.txt
         client_credentials=feed2toot_clientcred.txt
 
diff --git a/docs/source/configure.rst b/docs/source/configure.rst
index 53ff789..1d4a657 100644
--- a/docs/source/configure.rst
+++ b/docs/source/configure.rst
@@ -22,6 +22,7 @@ As described above, two files were created. You'll need them in the feed2toot co
 In order to configure Feed2toot, you need to create a feed2toot.ini file (or any name you prefer, finishing with the extension .ini) with the following parameters::
 
     [mastodon]
+    instance_url=https://mastodon.social
     ; Here you need the two files created by register_feed2toot_app
     user_credentials=/etc/feed2toot/credentials/feed2toot_usercred.txt
     client_credentials=/etc/feed2toot/credentials/feed2toot_clientcred.txt
@@ -43,6 +44,7 @@ In order to configure Feed2toot, you need to create a feed2toot.ini file (or any
 
 For the [mastodon] section:
 
+- instance_url: the url of your Mastodon instance
 - user_credentials: a file with the user credentials, generated by the command register_feed2toot_app
 - client_credentials: a file with the client credentials, generated by the command register_feed2toot_app