diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 4e67fbbe96d082f638420bd2a41e43e45a80a2df..10f2d17419cde1f2f7fa21fabc46fd87b694aae4 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -178,6 +178,7 @@ class QemuIoInteractive:
         cmd = cmd.strip()
         assert cmd != 'q' and cmd != 'quit'
         self._p.stdin.write(cmd + '\n')
+        self._p.stdin.flush()
         return self._read_output()