diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index d89f8388f..fa8ad33f5 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -834,6 +834,18 @@ void FileTransfer::download(FileTransferRequest && request, Sink & sink)
     }
 }
 
+template<typename... Args>
+FileTransferError::FileTransferError(FileTransfer::Error error, std::shared_ptr<string> response, const Args & ... args)
+    : Error(args...), error(error), response(response)
+{
+    const auto hf = hintfmt(args...);
+    if (response) {
+        err.hint = hintfmt("%1%\n\nresponse body:\n\n%2%", normaltxt(hf.str()), response);
+    } else {
+        err.hint = hf;
+    }
+}
+
 bool isUri(const string & s)
 {
     if (s.compare(0, 8, "channel:") == 0) return true;
diff --git a/src/libstore/filetransfer.hh b/src/libstore/filetransfer.hh
index 8e31a9e42..25ade0add 100644
--- a/src/libstore/filetransfer.hh
+++ b/src/libstore/filetransfer.hh
@@ -104,10 +104,11 @@ class FileTransferError : public Error
 public:
     FileTransfer::Error error;
     std::shared_ptr<string> response; // intentionally optional
+
     template<typename... Args>
-    FileTransferError(FileTransfer::Error error, std::shared_ptr<string> response, const Args & ... args)
-        : Error(args...), error(error), response(response)
-    { }
+    FileTransferError(FileTransfer::Error error, std::shared_ptr<string> response, const Args & ... args);
+
+    virtual const char* sname() const override { return "FileTransferError"; }
 };
 
 bool isUri(const string & s);
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 1e6102ce1..ac9d2e494 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -173,9 +173,8 @@ public:
 
     template<typename... Args>
     SysError(const Args & ... args)
-      :Error("")
+        : Error(""), errNo(errno)
     {
-        errNo = errno;
         auto hf = hintfmt(args...);
         err.hint = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo));
     }