diff --git a/manifests/apt_conf.pp b/manifests/apt_conf.pp
index f446c69..01540de 100644
--- a/manifests/apt_conf.pp
+++ b/manifests/apt_conf.pp
@@ -25,7 +25,7 @@ define apt::apt_conf(
     mode   => '0644',
   }
 
-  if $source {
+  if $source != '' {
     File["/etc/apt/apt.conf.d/${name}"] {
       source => $source,
     }