diff --git a/nix/rt.nix b/nix/rt.nix
index ea3e076..af49a7c 100644
--- a/nix/rt.nix
+++ b/nix/rt.nix
@@ -82,7 +82,7 @@ let
         last.nodes
         pkgs.strace
       ];
-      preConfigure = ''
+      preConfigure = old.preConfigure + ''
         export NODES_HOME="${last.nodes}"
         export NANOS6_HOME="${last.nanos6}"
       '';