diff --git a/tools/build/build.py b/tools/build/build.py
index 8ec7a7c0..7433ceb8 100755
--- a/tools/build/build.py
+++ b/tools/build/build.py
@@ -96,6 +96,7 @@ def build_oxjs(downloads=False, geo=False):
             '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
+            'Object.js', # Ox.typeOf depends on Ox.hasOwn
             'Type.js' # Ox.slice may depend on Ox.typeOf
         ]
     ]