diff --git a/include/libcamera/base/flags.h b/include/libcamera/base/flags.h
index a1b404bd..43afdf26 100644
--- a/include/libcamera/base/flags.h
+++ b/include/libcamera/base/flags.h
@@ -137,6 +137,9 @@ public:
 	}
 
 private:
+	template<typename>
+	friend class IPADataSerializer;
+
 	Type value_;
 };