Index: src/runtime/class.m
==================================================================
--- src/runtime/class.m
+++ src/runtime/class.m
@@ -333,11 +333,13 @@
 	 * in the initialize method
 	 */
 	class->info |= OBJC_CLASS_INFO_INITIALIZED;
 	class->isa->info |= OBJC_CLASS_INFO_INITIALIZED;
 
-	callMethod(class, "initialize");
+	if (class_respondsToSelector(object_getClass(class),
+	    @selector(initialize)))
+		[class initialize];
 }
 
 void
 objc_initialize_class(Class class)
 {

Index: src/runtime/lookup.m
==================================================================
--- src/runtime/lookup.m
+++ src/runtime/lookup.m
@@ -22,19 +22,10 @@
 
 #import "ObjFW_RT.h"
 #import "private.h"
 #import "macros.h"
 
-@interface DummyObject
-{
-	Class isa;
-}
-
-+ (bool)resolveClassMethod: (SEL)selector;
-+ (bool)resolveInstanceMethod: (SEL)selector;
-@end
-
 static IMP forwardHandler = (IMP)0;
 static IMP stretForwardHandler = (IMP)0;
 
 static IMP
 commonMethodNotFound(id object, SEL selector, IMP (*lookup)(id, SEL),

Index: src/runtime/private.h
==================================================================
--- src/runtime/private.h
+++ src/runtime/private.h
@@ -276,5 +276,15 @@
 		fprintf(stderr, "\n");					\
 		fflush(stderr);						\
 		abort();						\
 		OF_UNREACHABLE						\
 	}
+
+@interface DummyObject
+{
+	Class _Nonnull isa;
+}
+
++ (void)initialize;
++ (bool)resolveClassMethod: (nonnull SEL)selector;
++ (bool)resolveInstanceMethod: (nonnull SEL)selector;
+@end