diff --git a/tests/test_monitoring.py b/tests/test_monitoring.py
index 637a5e1c90954802185af332adf93724311eec9c..999d787f04b094fcb90194a1720da61ef8127b6e 100755
--- a/tests/test_monitoring.py
+++ b/tests/test_monitoring.py
@@ -45,7 +45,7 @@ def check_munin():
     mtime = os.path.getmtime(MUNIN_CHECK_PATH)
     d = datetime.fromtimestamp(mtime)
     now = datetime.now()
-    diff_seconds = (now - d).total_seconds
+    diff_seconds = (now - d).total_seconds()
     if diff_seconds > 3600:
         print_red('Monitoring data is older than 1 hour and is probably not working.')
         return 1