diff --git a/src/util.h b/src/util.h
index 1b94bc2fc5..86ef1101cd 100644
--- a/src/util.h
+++ b/src/util.h
@@ -61,6 +61,10 @@ extern HeapLeakChecker* heap_checker;
 #include <pthread_np.h>
 #endif
 
+#define FORWARD_DECLARE_NAMESPACED(cls, ns) \
+	namespace ns { class cls; } \
+	using cls [[deprecated("Remove in v4.1. Use " #ns "::" #cls " instead.")]] = ns::cls;
+
 [[deprecated("Remove in v4.1. Use uint64_t instead.")]]
 typedef uint64_t uint64;
 [[deprecated("Remove in v4.1. Use uint32_t instead.")]]