diff --git a/tools/test-run-dev b/tools/test-run-dev
index 4da2292eac..005b0acf0f 100755
--- a/tools/test-run-dev
+++ b/tools/test-run-dev
@@ -44,7 +44,7 @@ def test_nagios(nagios_logfile):
         '--nagios',
         '--site=127.0.0.1:9991',
     ]
-    result = subprocess.check_output(args, env=my_env,
+    result = subprocess.check_output(args, env=my_env, universal_newlines=True,
                                      stderr=nagios_logfile)
 
     if 'success' in result: