Index: newforms/formsets.py
===================================================================
--- newforms/formsets.py	(revision 5671)
+++ newforms/formsets.py	(working copy)
@@ -147,7 +147,7 @@
 
     def is_valid(self):
         self.full_clean()
-        return self._is_valid
+        return self.is_bound and self._is_valid
 
 def formset_for_form(form, formset=BaseFormSet, num_extra=1, orderable=False, deletable=False):
     """Return a FormSet for the given form class."""
@@ -159,4 +159,4 @@
     for formset in formsets:
         if not formset.is_valid():
             return False
-    return True
\ No newline at end of file
+    return True