diff --git a/nixos/lib/test-driver/test-driver.py b/nixos/lib/test-driver/test-driver.py
index 156392ad1e3..68bd35dd98e 100644
--- a/nixos/lib/test-driver/test-driver.py
+++ b/nixos/lib/test-driver/test-driver.py
@@ -110,7 +110,6 @@ def create_vlan(vlan_nr: str) -> Tuple[str, str, "subprocess.Popen[bytes]", Any]
     pty_master, pty_slave = pty.openpty()
     vde_process = subprocess.Popen(
         ["vde_switch", "-s", vde_socket, "--dirmode", "0700"],
-        bufsize=1,
         stdin=pty_slave,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
@@ -748,7 +747,6 @@ class Machine:
 
         self.process = subprocess.Popen(
             self.script,
-            bufsize=1,
             stdin=subprocess.DEVNULL,
             stdout=subprocess.PIPE,
             stderr=subprocess.STDOUT,