diff --git a/tests/filtertraceback.py b/tests/filtertraceback.py
--- a/tests/filtertraceback.py
+++ b/tests/filtertraceback.py
@@ -4,8 +4,19 @@
 
 from __future__ import absolute_import, print_function
 
+import io
 import sys
 
+if sys.version_info[0] >= 3:
+    # Prevent \r from being inserted on Windows.
+    sys.stdout = io.TextIOWrapper(
+        sys.stdout.buffer,
+        sys.stdout.encoding,
+        sys.stdout.errors,
+        newline="\n",
+        line_buffering=sys.stdout.line_buffering,
+    )
+
 state = 'none'
 
 for line in sys.stdin: