Index: src/runtime/class.m
==================================================================
--- src/runtime/class.m
+++ src/runtime/class.m
@@ -160,10 +160,36 @@
 		    cls->superclass->name);
 
 	cls->superclass->subclass_list[i] = cls;
 	cls->superclass->subclass_list[i + 1] = Nil;
 }
+
+static void
+setup_class(Class cls)
+{
+	const char *superclass;
+
+	if (cls->info & OBJC_CLASS_INFO_SETUP)
+		return;
+
+	if ((superclass = ((struct objc_abi_class*)cls)->superclass) != NULL) {
+		if ((cls->superclass = objc_lookup_class(superclass)) == Nil)
+			return;
+
+		cls->isa->superclass = cls->superclass->isa;
+
+		add_subclass(cls);
+		add_subclass(cls->isa);
+	} else
+		cls->isa->superclass = cls;
+
+	objc_update_dtable(cls);
+	objc_update_dtable(cls->isa);
+
+	cls->info |= OBJC_CLASS_INFO_SETUP;
+	cls->isa->info |= OBJC_CLASS_INFO_SETUP;
+}
 
 inline Class
 objc_classname_to_class(const char *name)
 {
 	Class c;
@@ -196,11 +222,10 @@
 
 inline Class
 objc_lookup_class(const char *name)
 {
 	Class cls = objc_classname_to_class(name);
-	const char *superclass;
 
 	if (cls == NULL)
 		return Nil;
 
 	if (cls->info & OBJC_CLASS_INFO_INITIALIZED)
@@ -216,26 +241,18 @@
 	if (cls->info & OBJC_CLASS_INFO_INITIALIZED) {
 		objc_global_mutex_unlock();
 		return cls;
 	}
 
-	if ((superclass = ((struct objc_abi_class*)cls)->superclass) != NULL) {
-		if ((cls->superclass = objc_lookup_class(superclass)) == Nil) {
-			objc_global_mutex_unlock();
-			return Nil;
-		}
-
-		cls->isa->superclass = cls->superclass->isa;
-
-		add_subclass(cls);
-		add_subclass(cls->isa);
-	} else
-		cls->isa->superclass = cls;
-
-	objc_update_dtable(cls);
-	objc_update_dtable(cls->isa);
-
+	setup_class(cls);
+
+	if (!(cls->info & OBJC_CLASS_INFO_SETUP)) {
+		objc_global_mutex_unlock();
+		return Nil;
+	}
+
+	/* Set it first to prevent calling it recursively */
 	cls->info |= OBJC_CLASS_INFO_INITIALIZED;
 	cls->isa->info |= OBJC_CLASS_INFO_INITIALIZED;
 
 	call_initialize(cls);
 

Index: src/runtime/runtime-private.h
==================================================================
--- src/runtime/runtime-private.h
+++ src/runtime/runtime-private.h
@@ -117,11 +117,13 @@
 };
 
 enum objc_abi_class_info {
 	OBJC_CLASS_INFO_CLASS	    = 0x01,
 	OBJC_CLASS_INFO_METACLASS   = 0x02,
-	OBJC_CLASS_INFO_INITIALIZED = 0x04
+	OBJC_CLASS_INFO_SETUP	    = 0x04,
+	OBJC_CLASS_INFO_LOADED	    = 0x08,
+	OBJC_CLASS_INFO_INITIALIZED = 0x10
 };
 
 typedef struct {
 	of_mutex_t mutex;
 	of_thread_t owner;