Index: src/block.h
==================================================================
--- src/block.h
+++ src/block.h
@@ -40,14 +40,15 @@
 extern "C" {
 #endif
 extern void *_Block_copy(const void *);
 extern void _Block_release(const void *);
 
-# if defined(OF_WINDOWS) && defined(OF_COMPILING_OBJFW)
+# ifdef OF_WINDOWS
 /*
  * Clang has implicit declarations for these, but they are dllimport. When
- * compiling ObjFW itself, these need to be dllexport.
+ * compiling ObjFW itself or using it as a static library, these need to be
+ * dllexport. Interestingly, this still works when using it as a shared library.
  */
 extern __declspec(dllexport) struct objc_abi_class _NSConcreteStackBlock;
 extern __declspec(dllexport) struct objc_abi_class _NSConcreteGlobalBlock;
 extern __declspec(dllexport) void _Block_object_assign(void *, const void *,
     const int);

Index: tests/OFBlockTests.m
==================================================================
--- tests/OFBlockTests.m
+++ tests/OFBlockTests.m
@@ -28,13 +28,13 @@
 
 #import "TestsAppDelegate.h"
 
 static OFString *module = @"OFBlock";
 
-extern void *_NSConcreteStackBlock;
-extern void *_NSConcreteGlobalBlock;
-extern void *_NSConcreteMallocBlock;
+extern struct objc_abi_class _NSConcreteStackBlock;
+extern struct objc_abi_class _NSConcreteGlobalBlock;
+extern struct objc_abi_class _NSConcreteMallocBlock;
 
 static void (^g)(void) = ^ {};
 
 static int
 (^returnStackBlock(void))(void)