diff --git a/file_handler.hpp b/file_handler.hpp
index c419949..64be8bf 100644
--- a/file_handler.hpp
+++ b/file_handler.hpp
@@ -28,6 +28,7 @@
     void close() override;
     bool write(std::uint32_t offset,
                const std::vector<std::uint8_t>& data) override;
+    int getSize() override;
 
   private:
     /** the active hash path, ignore. */