diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index 5ec57efad1..90ca262171 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -3386,6 +3386,7 @@ public class MessageHelper {
                     }
 
                 else if (local.isCompressed()) {
+                    // https://commons.apache.org/proper/commons-compress/examples.html
                     SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
                     boolean unzip = prefs.getBoolean("unzip", true);