diff --git a/tools/test.py b/tools/test.py
index 452b99edbc4024..59a31bf1cfabe4 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -1418,7 +1418,7 @@ def Main():
   logger.addHandler(ch)
   logger.setLevel(logging.INFO)
   if options.logfile:
-    fh = logging.FileHandler(options.logfile)
+    fh = logging.FileHandler(options.logfile, mode='wb')
     logger.addHandler(fh)
 
   workspace = abspath(join(dirname(sys.argv[0]), '..'))