Index: src/runtime/class.m
==================================================================
--- src/runtime/class.m
+++ src/runtime/class.m
@@ -26,18 +26,25 @@
 #import "runtime-private.h"
 
 static struct objc_hashtable *classes = NULL;
 static Class *load_queue = NULL;
 static size_t load_queue_cnt = 0;
+static struct objc_sparsearray *empty_dtable = NULL;
 
 static void
 register_class(struct objc_abi_class *cls)
 {
 	if (classes == NULL)
 		classes = objc_hashtable_alloc(2);
 
 	objc_hashtable_set(classes, cls->name, cls);
+
+	if (empty_dtable == NULL)
+		empty_dtable = objc_sparsearray_new();
+
+	cls->dtable = empty_dtable;
+	cls->metaclass->dtable = empty_dtable;
 }
 
 BOOL
 class_registerAlias_np(Class cls, const char *name)
 {
@@ -128,11 +135,14 @@
 {
 	struct objc_method_list *ml;
 	struct objc_category **cats;
 	unsigned int i;
 
-	if (cls->dtable == NULL)
+	if (!(cls->info & OBJC_CLASS_INFO_INITIALIZED))
+		return;
+
+	if (cls->dtable == empty_dtable)
 		cls->dtable = objc_sparsearray_new();
 
 	if (cls->superclass != Nil)
 		objc_sparsearray_copy(cls->dtable, cls->superclass->dtable);
 
@@ -217,13 +227,10 @@
 		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;
 }
 
 static void
@@ -240,12 +247,45 @@
 	 * in the initialize method
 	 */
 	cls->info |= OBJC_CLASS_INFO_INITIALIZED;
 	cls->isa->info |= OBJC_CLASS_INFO_INITIALIZED;
 
+	objc_update_dtable(cls);
+	objc_update_dtable(cls->isa);
+
 	call_method(cls, "initialize");
 }
+
+void
+objc_initialize_class(Class cls)
+{
+	if (cls->info & OBJC_CLASS_INFO_INITIALIZED)
+		return;
+
+	objc_global_mutex_lock();
+
+	/*
+	 * It's possible that two threads try to initialize a class at the same
+	 * time. Make sure that the thread which held the lock did not already
+	 * initialize it.
+	 */
+	if (cls->info & OBJC_CLASS_INFO_INITIALIZED) {
+		objc_global_mutex_unlock();
+		return;
+	}
+
+	setup_class(cls);
+
+	if (!(cls->info & OBJC_CLASS_INFO_SETUP)) {
+		objc_global_mutex_unlock();
+		return;
+	}
+
+	initialize_class(cls);
+
+	objc_global_mutex_unlock();
+}
 
 void
 objc_register_all_classes(struct objc_abi_symtab *symtab)
 {
 	uint_fast32_t i;
@@ -317,35 +357,21 @@
 	Class cls = objc_classname_to_class(name);
 
 	if (cls == NULL)
 		return Nil;
 
-	if (cls->info & OBJC_CLASS_INFO_INITIALIZED)
+	if (cls->info & OBJC_CLASS_INFO_SETUP)
 		return cls;
 
 	objc_global_mutex_lock();
 
-	/*
-	 * It's possible that two threads try to get a class at the same time.
-	 * Make sure that the thread which held the lock did not already
-	 * initialize it.
-	 */
-	if (cls->info & OBJC_CLASS_INFO_INITIALIZED) {
-		objc_global_mutex_unlock();
-		return cls;
-	}
-
 	setup_class(cls);
 
-	if (!(cls->info & OBJC_CLASS_INFO_SETUP)) {
-		objc_global_mutex_unlock();
-		return Nil;
-	}
-
-	initialize_class(cls);
-
-	objc_global_mutex_unlock();
+	objc_global_mutex_unlock();
+
+	if (!(cls->info & OBJC_CLASS_INFO_SETUP))
+		return Nil;
 
 	return cls;
 }
 
 Class

Index: src/runtime/lookup.m
==================================================================
--- src/runtime/lookup.m
+++ src/runtime/lookup.m
@@ -26,10 +26,33 @@
 IMP (*objc_forward_handler)(id, SEL) = NULL;
 
 IMP
 objc_not_found_handler(id obj, SEL sel)
 {
+	if (!(obj->isa->info & OBJC_CLASS_INFO_INITIALIZED)) {
+		BOOL is_class = obj->isa->info & OBJC_CLASS_INFO_METACLASS;
+		Class cls = (is_class ? (Class)obj : obj->isa);
+
+		objc_initialize_class(cls);
+
+		if (!(cls->info & OBJC_CLASS_INFO_SETUP)) {
+			if (is_class)
+				return objc_msg_lookup(nil, sel);
+			else
+				ERROR("Could not dispatch message for "
+				    "incomplete class %s!", cls->name);
+		}
+
+		/*
+		 * We don't need to handle the case that super was called.
+		 * The reason for this is that a call to super is not possible
+		 * before a message to the class has been sent and it thus has
+		 * been initialized together with its superclasses.
+		 */
+		return objc_msg_lookup(obj, sel);
+	}
+
 	if (objc_forward_handler != NULL)
 		return objc_forward_handler(obj, sel);
 
 	ERROR("Selector %s is not implemented for class %s!",
 	    sel_getName(sel), obj->isa->name);

Index: src/runtime/runtime-private.h
==================================================================
--- src/runtime/runtime-private.h
+++ src/runtime/runtime-private.h
@@ -139,10 +139,11 @@
 } objc_mutex_t;
 
 extern void objc_register_all_categories(struct objc_abi_symtab*);
 extern struct objc_category** objc_categories_for_class(Class);
 extern void objc_free_all_categories(void);
+extern void objc_initialize_class(Class);
 extern void objc_update_dtable(Class);
 extern void objc_register_all_classes(struct objc_abi_symtab*);
 extern Class objc_classname_to_class(const char*);
 extern void objc_free_all_classes(void);
 extern uint32_t objc_hash_string(const char*);