diff --git a/test/etc_network_interfaces/runtest.pl b/test/etc_network_interfaces/runtest.pl
index b5277c3..f92f5ae 100755
--- a/test/etc_network_interfaces/runtest.pl
+++ b/test/etc_network_interfaces/runtest.pl
@@ -9,6 +9,7 @@ use Carp;
 use POSIX;
 use IO::Handle;
 use Storable qw(dclone);
+use JSON; # allows simple debug-dumping of variables  `print to_json($foo, {pretty => 1}) ."\n"`
 
 use PVE::INotify;