--- orig/etc/apt/apt.conf.d/20-clean
+++ mod/etc/apt/apt.conf.d/20-clean
@@ -3,6 +3,17 @@
   Clean-Installed "false";
 };
 
+Binary
+{
+  apt
+  {
+    APT
+    {
+      Keep-Downloaded-Packages "true";
+    };
+  };
+};
+
 DSelect
 {
   Clean "auto";
