Index: src/runtime/runtime.h
==================================================================
--- src/runtime/runtime.h
+++ src/runtime/runtime.h
@@ -139,20 +139,23 @@
 	struct objc_object *obj = (struct objc_object*)obj_;
 
 	return obj->isa;
 }
 
-static inline void
+static inline Class
 object_setClass(id obj_, Class cls)
 {
 	struct objc_object *obj = (struct objc_object*)obj_;
+	Class old = obj->isa;
 
 	obj->isa = cls;
+
+	return old;
 }
 
 static inline const char*
 object_getClassName(id obj)
 {
 	return class_getName(object_getClass(obj));
 }
 
 #endif