Index: tests/OFBlockTests.m
==================================================================
--- tests/OFBlockTests.m
+++ tests/OFBlockTests.m
@@ -19,13 +19,19 @@
 
 #import "TestsAppDelegate.h"
 
 static OFString *module = @"OFBlock";
 
+#if defined(OF_OBJFW_RUNTIME)
 extern struct objc_class _NSConcreteStackBlock;
 extern struct objc_class _NSConcreteGlobalBlock;
 extern struct objc_class _NSConcreteMallocBlock;
+#elif defined(OF_APPLE_RUNTIME)
+extern void *_NSConcreteStackBlock;
+extern void *_NSConcreteGlobalBlock;
+extern void *_NSConcreteMallocBlock;
+#endif
 
 static void (^g)(void) = ^ {};
 
 static int
 (^returnStackBlock(void))(void)