1 files changed, 6 insertions, 1 deletions
diff --git a/tests/helpers.py b/tests/helpers.py
index d652fe8e..be2484f3 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -22,10 +22,15 @@ def run_command(cmd):
     # In some strange cases (PyPy3 in a virtualenv!?) the stdout encoding of
     # the subprocess is set incorrectly to ascii.  Use an environment variable
     # to force the encoding to be the same as ours.
+    sub_env = dict(os.environ)
+    encoding = sys.__stdout__.encoding
+    if encoding:
+        sub_env['PYTHONIOENCODING'] = encoding
+
     proc = subprocess.Popen(
         cmd,
         shell=True,
-        env=dict(os.environ, PYTHONIOENCODING=sys.__stdout__.encoding),
+        env=sub_env,
         stdin=subprocess.PIPE, stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT
         )