diff --git a/src/libstore/include/nix/store/filetransfer.hh b/src/libstore/include/nix/store/filetransfer.hh
index 402ee4900..305c33af1 100644
--- a/src/libstore/include/nix/store/filetransfer.hh
+++ b/src/libstore/include/nix/store/filetransfer.hh
@@ -155,9 +155,10 @@ struct FileTransferRequest
         unreachable();
     }
 
+    void setupForS3();
+
 private:
     friend struct curlFileTransfer;
-    void setupForS3();
 #if NIX_WITH_AWS_AUTH
     std::optional<std::string> awsSigV4Provider;
 #endif