diff --git a/RoboFile.php b/RoboFile.php
index fb81a5c..7651a01 100644
--- a/RoboFile.php
+++ b/RoboFile.php
@@ -1,7 +1,6 @@
 <?php
 
 use Robo\Result;
-use splitbrain\PHPArchive\Zip;
 
 class RoboFile extends \Robo\Tasks {
     const BASE = __DIR__.\DIRECTORY_SEPARATOR;
@@ -209,45 +208,49 @@ class RoboFile extends \Robo\Tasks {
         // compile the stylesheet
         $t->taskExec($postcss)->arg($scss)->option("-o", $css);
         // download highlight.js
-        $t->addCode(function() use ($tmp, $themeout) {
-            $languages = ["php", "bash", "shell", "xml", "nginx", "apache"];
-            $post = http_build_query((function($langs) {
-                $out = [];
-                foreach($langs as $l) {
-                    $out[$l.".js"] = "on";
+        if (extension_loaded("zip")) {
+            $t->addCode(function() use ($tmp, $themeout) {
+                $languages = ["php", "bash", "shell", "xml", "nginx", "apache"];
+                $post = http_build_query((function($langs) {
+                    $out = [];
+                    foreach($langs as $l) {
+                        $out[$l.".js"] = "on";
+                    }
+                    return $out;
+                })($languages));
+                $conn = @fopen("https://highlightjs.org/download/", "r");
+                if ($conn === false) {
+                    throw new Exception("Unable to download Highlight.js");
                 }
-                return $out;
-            })($languages));
-            $conn = fopen("https://highlightjs.org/download/", "r");
-            if ($conn === false) {
-                throw new Exception("Unable to download Highlight.js");
-            }
-            foreach (stream_get_meta_data($conn)['wrapper_data'] as $field) {
-                if (preg_match("/^Set-Cookie: csrftoken=([^;]+)/i", $field, $cookie)) {
-                    break;
+                foreach (stream_get_meta_data($conn)['wrapper_data'] as $field) {
+                    if (preg_match("/^Set-Cookie: csrftoken=([^;]+)/i", $field, $cookie)) {
+                        break;
+                    }
                 }
-            }
-            $token = stream_get_contents($conn);
-            preg_match("/<input type='hidden' name='csrfmiddlewaretoken' value='([^']*)'/", $token, $token);
-            $post = "csrfmiddlewaretoken={$token[1]}&$post";
-            $hljs = file_get_contents("https://highlightjs.org/download/", false, stream_context_create(['http' => [
-                'method' => "POST",
-                'content' => $post,
-                'header' => [
-                    "Referer: https://highlightjs.org/download/",
-                    "Cookie: csrftoken={$cookie[1]}",
-                    "Content-Type: application/x-www-form-urlencoded",
-                ],
-            ]]));
-            if ($hljs === false) {
-                throw new Exception("Unable to download Highlight.js");
-            } else {
-                file_put_contents($tmp."highlightjs.zip", $hljs);
-            }
-            $z = new Zip;
-            $z->open($tmp."highlightjs.zip");
-            $z->extract($themeout, "", "", "highlight.pack.js");
-        }, "downloadHighlightjs");
+                $token = stream_get_contents($conn);
+                preg_match("/<input type='hidden' name='csrfmiddlewaretoken' value='([^']*)'/", $token, $token);
+                $post = "csrfmiddlewaretoken={$token[1]}&$post";
+                $hljs = @file_get_contents("https://highlightjs.org/download/", false, stream_context_create(['http' => [
+                    'method' => "POST",
+                    'content' => $post,
+                    'header' => [
+                        "Referer: https://highlightjs.org/download/",
+                        "Cookie: csrftoken={$cookie[1]}",
+                        "Content-Type: application/x-www-form-urlencoded",
+                    ],
+                ]]));
+                if ($hljs === false) {
+                    throw new Exception("Unable to download Highlight.js");
+                } else {
+                    file_put_contents($tmp."highlightjs.zip", $hljs);
+                }
+                $z = new \ZipArchive;
+                $z->open($tmp."highlightjs.zip");
+                $z->extractTo($themeout, "highlight.pack.js");
+            }, "downloadHighlightjs");
+        } else {
+            $this->say("Zip extension not installed; not updating hightlight.js");
+        }
         // execute the collection
         return $t->run();
     }