diff --git a/tools/build/build.py b/tools/build/build.py
index a86042a7..f35a9d25 100755
--- a/tools/build/build.py
+++ b/tools/build/build.py
@@ -87,11 +87,16 @@ def build_oxjs(downloads=False, geo=False):
                     write_link(link_source, link_target)
 
     # Ox.js
-    # FIXME: Document what exactly the following dependecies are!
     filenames = [
-        ['Fallback.js', 'Core.js'],
-        # Constants.js needs Ox.toArray to determine Ox.PATH
-        ['Array.js', 'Math.js']
+        [
+            'Core.js', # has to run first so that Ox is defined
+            'Fallback.js' # FIXME: not clear if needed here
+        ],
+        [
+            'Array.js', # Ox.PATH depends on Ox.toArray
+            'Collection.js', # Ox.toArray depends on Ox.slice
+            'Math.js' # Ox.MAX_LATITUDE depends on Ox.sinh
+        ]
     ]
     js = ''
     js_dir = 'Ox/js/'