diff --git a/PyNDN/Data.py b/PyNDN/Data.py
index 7e8dd56..5369380 100644
--- a/PyNDN/Data.py
+++ b/PyNDN/Data.py
@@ -101,7 +101,7 @@
                     # ?
                     pass
                 if value.freshnessSeconds:
-                    self._data.SetFreshness (ns.core.Seconds (value))
+                    self._data.SetFreshness (ns.core.Seconds (value.freshnessSeconds))
                 if value.keyLocator:
                     self._data.SetKeyLocator (value._name)
             else: