diff --git a/flask_security/utils.py b/flask_security/utils.py
index 547e231..91bd65f 100644
--- a/flask_security/utils.py
+++ b/flask_security/utils.py
@@ -196,7 +196,8 @@ def config_value(key, app=None, default=None):
 def get_max_age(key, app=None):
     now = datetime.utcnow()
     expires = now + get_within_delta(key + '_WITHIN', app)
-    return (expires - now).total_seconds()
+    td = (expires - now)
+    return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 1e6) / 1e6
 
 
 def get_within_delta(key, app=None):