diff --git a/fdroidserver/build.py b/fdroidserver/build.py
index 39bde47b..7e587c9b 100644
--- a/fdroidserver/build.py
+++ b/fdroidserver/build.py
@@ -79,7 +79,8 @@ def build_server(app, build, vcs, build_dir, output_dir, log_dir, force):
             buildserverid = subprocess.check_output(['vagrant', 'ssh', '-c',
                                                      'cat /home/vagrant/buildserverid'],
                                                     cwd='builder').rstrip()
-            logging.debug(_('Fetched buildserverid from VM: ') + buildserverid)
+            logging.debug(_('Fetched buildserverid from VM: {buildserverid}')
+                          .format(buildserverid=buildserverid.decode()))
 
         # Open SSH connection...
         logging.info("Connecting to virtual machine...")