diff --git a/docs/releases/1.2.txt b/docs/releases/1.2.txt
index 38df3b120c3..f30e84a77d2 100644
--- a/docs/releases/1.2.txt
+++ b/docs/releases/1.2.txt
@@ -299,6 +299,16 @@ For those following trunk, this change also applies to other decorators
 introduced since 1.1, including ``csrf_protect``, ``cache_control`` and anything
 created using ``decorator_from_middleware``.
 
+``ModelForm.is_valid()`` and ``ModelForm.errors``
+-------------------------------------------------
+
+Much of the validation work for ModelForms has been moved down to the model
+level. As a result, the first time you call ``ModelForm.is_valid()``, access
+``ModelForm.errors`` or otherwise trigger form validation, your model will be
+cleaned in-place. This conversion used to happen when the model was saved. If
+you need an unmodified instance of your model, you should pass a copy to the
+``ModelForm`` constructor.
+
 
 .. _deprecated-features-1.2:
 
diff --git a/docs/topics/forms/modelforms.txt b/docs/topics/forms/modelforms.txt
index 96ed0ab544f..9a649195346 100644
--- a/docs/topics/forms/modelforms.txt
+++ b/docs/topics/forms/modelforms.txt
@@ -196,6 +196,19 @@ we'll discuss in a moment.)::
         name = forms.CharField(max_length=100)
         authors = forms.ModelMultipleChoiceField(queryset=Author.objects.all())
 
+The ``is_valid()`` method and ``errors``
+----------------------------------------
+
+.. versionchanged:: 1.2
+
+The first time you call ``is_valid()`` or access the ``errors`` attribute of a
+``ModelForm`` has always triggered form validation, but as of Django 1.2, it
+will also trigger :ref:`model validation <validating-objects>`. This has the
+side-effect of cleaning the model you pass to the ``ModelForm`` constructor.
+For instance, calling ``is_valid()`` on your form will convert any date fields
+on your model to actual date objects.
+
+
 The ``save()`` method
 ---------------------