diff --git a/rpython/tool/ansi_print.py b/rpython/tool/ansi_print.py
index bfa40be..29dd332 100644
--- a/rpython/tool/ansi_print.py
+++ b/rpython/tool/ansi_print.py
@@ -7,7 +7,7 @@ from py.io import ansi_print
 from rpython.tool.ansi_mandelbrot import Driver
 
 
-isatty = getattr(sys.stderr, 'isatty', lambda: False)
+isatty = lambda: False
 mandelbrot_driver = Driver()
 wrote_dot = False     # global shared state