diff --git a/bob/devtools/build.py b/bob/devtools/build.py
index 262d944a5c454832a121918e6acc74ffc289079d..b284094f0d70ec92fa62b99d6b72649e9c81d6f1 100644
--- a/bob/devtools/build.py
+++ b/bob/devtools/build.py
@@ -454,6 +454,7 @@ if __name__ == '__main__':
 
   bootstrap.setup_logger(logger, args.verbose)
 
+  bootstrap.set_environment('PYTHONUNBUFFERED', '1')
   bootstrap.set_environment('DOCSERVER', bootstrap._SERVER)
   bootstrap.set_environment('LANG', 'en_US.UTF-8')
   bootstrap.set_environment('LC_ALL', os.environ['LANG'])