diff --git a/tools/build/build.py b/tools/build/build.py
index 83b5158c..2ae502e0 100755
--- a/tools/build/build.py
+++ b/tools/build/build.py
@@ -98,23 +98,20 @@ def build_oxjs(downloads=False, geo=False):
             'Core.js' # has to run first so that Ox is defined
         ],
         [
-            'Array.js', # Ox.PATH depends on Ox.toArray
-            'Collection.js', # Ox.toArray depends on Ox.slice
+            'Function.js', # getSortValue (Array.js) depends on Ox.cache
+            'Math.js', # Ox.MAX_LATITUDE (Constants.js) depends on Ox.sinh
             'Polyfill.js', # FIXME: not clear if needed here
-            'Math.js', # Ox.MAX_LATITUDE depends on Ox.sinh
-            'Object.js', # Ox.typeOf depends on Ox.hasOwn
-            'String.js', # HTML.js depends on Ox.char
-            'Type.js' # Ox.slice may depend on Ox.typeOf
         ]
     ]
     js = ''
     js_dir = 'Ox/js/'
-    ox_files = [[], [], []]
-    for filename in filenames[0]:
-        ox_files[0].append(js_dir + filename)
-    for filename in filenames[1]:
-        ox_files[1].append(js_dir + filename)
-    filenames = filenames[0] + filenames[1]
+    ox_files = []
+    for group in filenames:
+        ox_files.append([])
+        for filename in group:
+            ox_files[-1].append(js_dir + filename)
+    ox_files.append([])
+    filenames = sum(filenames, []) # flatten
     for filename in sorted(os.listdir(source_path + js_dir)):
         if not filename in filenames \
                 and not filename.startswith('.') \
@@ -122,8 +119,8 @@ def build_oxjs(downloads=False, geo=False):
             filenames.append(filename)
     for filename in filenames:
         js += read_file(source_path + js_dir + filename) + '\n'
-        if not js_dir + filename in ox_files[0] + ox_files[1]:
-            ox_files[2].append(js_dir + filename)
+        if not js_dir + filename in sum(ox_files, []):
+            ox_files[-1].append(js_dir + filename)
     js = re.sub("Ox.VERSION = '([\d\.]+)'", "Ox.VERSION = '%s'" % version, js)
     write_file(build_path + 'Ox.js', ox.js.minify(js, comment))
     write_file(dev_path + '/Ox/json/' + 'Ox.json', json.dumps({