diff --git a/src/cobj.c b/src/cobj.c
index bd6fc01..8daa5ba 100644
--- a/src/cobj.c
+++ b/src/cobj.c
@@ -250,6 +250,14 @@ void cosmoO_setObject(CState *state, CObjObject *object, CValue key, CValue val)
     }
 }
 
+void cosmoO_setUserData(CState *state, CObjObject *object, void *p) {
+    object->user = p;
+}
+
+void *cosmoO_getUserData(CState *state, CObjObject *object) {
+    return object->user;
+}
+
 bool cosmoO_getIString(CState *state, CObjObject *object, int flag, CValue *val) {
     if (readFlag(object->istringFlags, flag))
         return false; // it's been cached as bad
diff --git a/src/cobj.h b/src/cobj.h
index a3c365c..b5905ef 100644
--- a/src/cobj.h
+++ b/src/cobj.h
@@ -118,6 +118,9 @@ CObjUpval *cosmoO_newUpvalue(CState *state, CValue *val);
 bool cosmoO_getObject(CState *state, CObjObject *object, CValue key, CValue *val);
 void cosmoO_setObject(CState *state, CObjObject *object, CValue key, CValue val);
 
+void cosmoO_setUserData(CState *state, CObjObject *object, void *p);
+void *cosmoO_getUserData(CState *state, CObjObject *object);
+
 // internal string
 bool cosmoO_getIString(CState *state, CObjObject *object, int flag, CValue *val);