diff --git a/src/lib/Hydra/Helper/AddBuilds.pm b/src/lib/Hydra/Helper/AddBuilds.pm
index 734a97aa..6f51b98d 100644
--- a/src/lib/Hydra/Helper/AddBuilds.pm
+++ b/src/lib/Hydra/Helper/AddBuilds.pm
@@ -89,7 +89,7 @@ sub fetchInputBuild {
 
     if (!defined $prevBuild || !isValidPath(getMainOutput($prevBuild)->path)) {
         print STDERR "input `", $name, "': no previous build available\n";
-        return undef;
+        return ();
     }
 
     #print STDERR "input `", $name, "': using build ", $prevBuild->id, "\n";