diff --git a/README.md b/README.md
index 7ef40d0..4e6ea59 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,9 @@ require_once __DIR__ . '/vendor/autoload.php';
 use PhpAmqpLib\Connection\AMQPSSLConnection;
 use PhpAmqpLib\Message\AMQPMessage;
 
+define("NIX_SYSTEM", "x86_64-linux");
+define("WORKING_DIR", "/home/grahamc/.nix-test");
+
 function rabbitmq_conn() {
     $connection = new AMQPSSLConnection(
         'events.nix.gsc.io', 5671,
diff --git a/builder.php b/builder.php
index 81b8020..d4109ab 100644
--- a/builder.php
+++ b/builder.php
@@ -11,7 +11,7 @@ $channel->basic_qos(null, 1, true);
 list($queueName, , ) = $channel->queue_declare('build-results',
                                                false, true, false, false);
 
-list($queueName, , ) = $channel->queue_declare('build-inputs-x86_64-linux',
+list($queueName, , ) = $channel->queue_declare('build-inputs-' . NIX_SYSTEM,
                                                false, true, false, false);
 $channel->queue_bind($queueName, 'build-jobs');
 
@@ -21,7 +21,7 @@ function runner($msg) {
     $body = json_decode($msg->body);
     $in = $body->payload;
 
-    $co = new GHE\Checkout("/home/grahamc/.nix-test", "builder");
+    $co = new GHE\Checkout(WORKING_DIR, "builder");
     $pname = $co->checkOutRef($in->repository->full_name,
                               $in->repository->clone_url,
                               $in->issue->number,
diff --git a/mass-rebuilder.php b/mass-rebuilder.php
index 9be08ff..2831dbd 100644
--- a/mass-rebuilder.php
+++ b/mass-rebuilder.php
@@ -81,7 +81,7 @@ function runner($msg) {
 
         $against_name = "origin/" . $in->pull_request->base->ref;
         echo "Building against $against_name\n";
-        $co = new GHE\Checkout("/home/grahamc/.nix-test", "mr-est");
+        $co = new GHE\Checkout(WORKING_DIR, "mr-est");
     $pname = $co->checkOutRef($in->repository->full_name,
             $in->repository->clone_url,
             $in->number,