diff --git a/django/forms/fields.py b/django/forms/fields.py
index f5f3abf49d..dd5ae1e427 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -283,6 +283,11 @@ class DecimalField(Field):
         super(DecimalField, self).validate(value)
         if value in validators.EMPTY_VALUES:
             return
+        # Check for NaN, Inf and -Inf values. We can't compare directly for NaN,
+        # since it is never equal to itself. However, NaN is the only value that
+        # isn't equal to itself, so we can use this to identify NaN
+        if value != value or value == Decimal("Inf") or value == Decimal("-Inf"):
+            raise ValidationError(self.error_messages['invalid'])
         sign, digittuple, exponent = value.as_tuple()
         decimals = abs(exponent)
         # digittuple doesn't include any leading zeros.
@@ -467,7 +472,7 @@ class ImageField(FileField):
         f = super(ImageField, self).to_python(data)
         if f is None:
             return None
-            
+
         # Try to import PIL in either of the two ways it can end up installed.
         try:
             from PIL import Image
@@ -584,7 +589,7 @@ class ChoiceField(Field):
 
     def __init__(self, choices=(), required=True, widget=None, label=None,
                  initial=None, help_text=None, *args, **kwargs):
-        super(ChoiceField, self).__init__(required=required, widget=widget, label=label, 
+        super(ChoiceField, self).__init__(required=required, widget=widget, label=label,
                                         initial=initial, help_text=help_text, *args, **kwargs)
         self.choices = choices
 
diff --git a/tests/regressiontests/forms/fields.py b/tests/regressiontests/forms/fields.py
index d5eccfcee7..0c7493ee67 100644
--- a/tests/regressiontests/forms/fields.py
+++ b/tests/regressiontests/forms/fields.py
@@ -203,6 +203,9 @@ class FieldsTests(TestCase):
         self.assertEqual(f.clean('3.14'), Decimal("3.14"))
         self.assertEqual(f.clean(3.14), Decimal("3.14"))
         self.assertEqual(f.clean(Decimal('3.14')), Decimal("3.14"))
+        self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a number.']", f.clean, 'NaN')
+        self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a number.']", f.clean, 'Inf')
+        self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a number.']", f.clean, '-Inf')
         self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a number.']", f.clean, 'a')
         self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a number.']", f.clean, u'łąść')
         self.assertEqual(f.clean('1.0 '), Decimal("1.0"))
@@ -498,7 +501,7 @@ class FieldsTests(TestCase):
         # hangs "forever" if catastrophic backtracking in ticket:#11198 not fixed
         self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a valid URL.']", f.clean, 'http://%s' % ("X"*200,))
 
-        # a second test, to make sure the problem is really addressed, even on 
+        # a second test, to make sure the problem is really addressed, even on
         # domains that don't fail the domain label length check in the regex
         self.assertRaisesErrorWithMessage(ValidationError, "[u'Enter a valid URL.']", f.clean, 'http://%s' % ("X"*60,))