diff --git a/vobject/icalendar.py b/vobject/icalendar.py
index a44fffb..ba5f073 100644
--- a/vobject/icalendar.py
+++ b/vobject/icalendar.py
@@ -1913,13 +1913,15 @@ def error(msg):
                                                sec))
                 current = ""
                 sign = None
-                week = None
-                day = None
-                hour = None
-                minute = None
-                sec = None
+                week = 0
+                day = 0
+                hour = 0
+                minute = 0
+                sec = 0
             elif char == "eof":
                 state = "end"
+                if not current:
+                    second = '0'
             else:
                 state = "error"
                 error("got unexpected character reading in duration: " + s)