diff --git a/ci/upload_coverage.py b/ci/upload_coverage.py
index 1d46c8568..106a6d045 100644
--- a/ci/upload_coverage.py
+++ b/ci/upload_coverage.py
@@ -35,9 +35,9 @@ def run_with_python(args, **kwargs):
     msg("Running:", *cmd)
     res = run(cmd, check=True, stdout=PIPE, stderr=PIPE, **kwargs)
     msg("STDOUT:")
-    msg(res.stdout)
+    sys.stdout.buffer.write(res.stdout)
     msg("STDERR:")
-    msg(res.stdout)
+    sys.stderr.buffer.write(res.stdout)
     return res