diff --git a/clients/tests/test-client.py b/clients/tests/test-client.py
index fdd21d544d..0ca7300401 100755
--- a/clients/tests/test-client.py
+++ b/clients/tests/test-client.py
@@ -764,7 +764,7 @@ class TestNmcli(NmTestBase):
                     self.fail("Unexpected output of command, expected %s. Rerun test with NM_TEST_REGENERATE=1 to regenerate files" % (filename))
 
         if regenerate:
-            content_new = ''.join([r['content'] for r in results])
+            content_new = b''.join([r['content'] for r in results])
             if content_new != content_expect:
                 try:
                     with open(filename, 'wb') as content_file: