diff --git a/apt/manifests/init.pp b/apt/manifests/init.pp
index f43f494..e81afdc 100644
--- a/apt/manifests/init.pp
+++ b/apt/manifests/init.pp
@@ -173,7 +173,7 @@ define apt::repo($source, $dist="", $components="main", $key="", $keyserver="")
     }
 
     if $apt_proxy {
-        $source_real = regsubst($source, "^([^:]+://)(.+)$", "\1$apt_proxy/\2")
+        $source_real = regsubst($source, "^([^:]+://)(.+)$", "\\1$apt_proxy/\\2")
     } else {
         $source_real = $source
     }