diff --git a/qubesadmin/backup/restore.py b/qubesadmin/backup/restore.py
index f0130477..36b05592 100644
--- a/qubesadmin/backup/restore.py
+++ b/qubesadmin/backup/restore.py
@@ -1195,15 +1195,16 @@ def _retrieve_backup_header_files(self, files, allow_none=False):
         retrieve_proc_returncode = retrieve_proc.wait()
         if retrieve_proc in self.processes_to_kill_on_cancel:
             self.processes_to_kill_on_cancel.remove(retrieve_proc)
-        extract_stderr = error_pipe.read(MAX_STDERR_BYTES)
+        extract_stderr = error_pipe.read(MAX_STDERR_BYTES).decode(
+            'ascii', 'ignore')
         error_pipe.close()
 
         # wait for other processes (if any)
         for proc in self.processes_to_kill_on_cancel:
             if proc.wait() != 0:
                 raise QubesException(
-                    "Backup header retrieval failed (exit code {})".format(
-                        proc.wait())
+                    "Backup header retrieval failed (exit code {}): {}".format(
+                        proc.wait(), extract_stderr)
                 )
 
         if retrieve_proc_returncode != 0: