diff --git a/ipython_magic/datemagic.py b/ipython_magic/datemagic.py
index 493ac54..c2c77a7 100644
--- a/ipython_magic/datemagic.py
+++ b/ipython_magic/datemagic.py
@@ -53,7 +53,7 @@ class DateMagic(Magics):
     @argument('-z', '--timezone', action='store_true', help='prints time zone')
     @argument('-y', '--python', action='store_true', help='prints Python version')
     @argument('-i', '--ipython', action='store_true', help='prints IPython version')
-    @argument('-p', '--packages', action=str, help='prints versions of Python modules and packages')
+    @argument('-p', '--packages', type=str, help='prints versions of Python modules and packages')
     def date(self, line):
         """ 
         IPython magic function for printing the current date, time, Python,