diff --git a/kitty_tests/prewarm.py b/kitty_tests/prewarm.py
index 50bb38ad2..1692e58fe 100644
--- a/kitty_tests/prewarm.py
+++ b/kitty_tests/prewarm.py
@@ -91,7 +91,7 @@ def socket_child_main(exit_code=0, initial_print=''):
         pty.wait_till(lambda: 'child ready:' in pty.screen_contents())
         pty.set_window_size(columns=cols + 3)
         pty.wait_till(lambda: f'Screen size changed: {cols + 3}' in pty.screen_contents())
-        pty.write_to_child('\x03')
+        pty.write_to_child('\x03' * 64)
         pty.wait_till(lambda: 'KeyboardInterrupt' in pty.screen_contents(), timeout=30)
         wait_for_death(signal.SIGINT)