@@ -45,10 +45,16 @@
 } alloc_failed_exception;
 
 #ifdef NEED_OBJC_SYNC_INIT
 extern BOOL objc_sync_init();
 #endif
+
+void
+enumeration_mutation_handler(id object)
+{
+	@throw [OFEnumerationMutationException newWithClass: [object class]];
+}
 
 @implementation OFObject
 + (void)load
 {
 #ifdef NEED_OBJC_SYNC_INIT
@@ -55,10 +61,14 @@
 	if (!objc_sync_init()) {
 		fputs("Runtime error: objc_sync_init() failed!\n", stderr);
 		abort();
 	}
 #endif
+
+#ifdef OF_APPLE_RUNTIME
+	objc_setEnumerationMutationHandler(enumeration_mutation_handler);
+#endif
 }
 
 + (void)initialize
 {
 }