diff --git a/src/libstore/http-binary-cache-store.cc b/src/libstore/http-binary-cache-store.cc
index 74ae7a4d..9d31f77c 100644
--- a/src/libstore/http-binary-cache-store.cc
+++ b/src/libstore/http-binary-cache-store.cc
@@ -71,7 +71,7 @@ protected:
 
     void getFile(const std::string & path,
         std::function<void(std::shared_ptr<std::string>)> success,
-        std::function<void(std::exception_ptr exc)> failure)
+        std::function<void(std::exception_ptr exc)> failure) override
     {
         DownloadRequest request(cacheUri + "/" + path);
         request.showProgress = DownloadRequest::no;