diff --git a/tests/test_bin.py b/tests/test_bin.py
index 0eab72e..55a23b2 100644
--- a/tests/test_bin.py
+++ b/tests/test_bin.py
@@ -39,8 +39,8 @@ def run_cmd(cmd, stdin_data=None):
     # Read stdout and stderr otherwise if the PIPE buffer is full, we might
     # wait for ever…
     while p.poll() is None:
-        stdout += str(p.stdout.read())
-        stderr += str(p.stderr.read())
+        stdout += p.stdout.read().decode('utf-8')
+        stderr += p.stderr.read().decode('utf-8')
     return p.returncode, stdout, stderr