diff --git a/tests/test-context.py b/tests/test-context.py
--- a/tests/test-context.py
+++ b/tests/test-context.py
@@ -7,7 +7,7 @@ repo = hg.repository(u, 'test1', create=
 os.chdir('test1')
 
 # create 'foo' with fixed time stamp
-f = open('foo', 'w')
+f = open('foo', 'wb')
 f.write('foo\n')
 f.close()
 os.utime('foo', (1000, 1000))