gistfile1.txt

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 91ecbf2..18e62ef 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -928,6 +928,11 @@ class IPAddressField(Field):
         kwargs['max_length'] = 15
         Field.__init__(self, *args, **kwargs)
 
+    def get_db_prep_value(self, value, connection, prepared=False):
+        if not prepared:
+            value = self.get_prep_value(value)
+        return value or None
+
     def get_internal_type(self):
         return "IPAddressField"
 
diff --git a/tests/regressiontests/model_fields/models.py b/tests/regressiontests/model_fields/models.py
index 1dc1649..f75da1f 100644
--- a/tests/regressiontests/model_fields/models.py
+++ b/tests/regressiontests/model_fields/models.py
@@ -158,3 +158,6 @@ if Image:
                                   width_field='headshot_width')
 
 ###############################################################################
+
+class IPLog(models.Model):
+    ip = models.IPAddressField(blank=True, null=True)
diff --git a/tests/regressiontests/model_fields/tests.py b/tests/regressiontests/model_fields/tests.py
index b42c0af..a03ab31 100644
--- a/tests/regressiontests/model_fields/tests.py
+++ b/tests/regressiontests/model_fields/tests.py
@@ -8,7 +8,8 @@ from django.db import models
 from django.db.models.fields.files import FieldFile
 from django.utils import unittest
 
-from models import Foo, Bar, Whiz, BigD, BigS, Image, BigInt, Post, NullBooleanModel, BooleanModel, Document
+from models import (Foo, Bar, Whiz, BigD, BigS, Image, BigInt, Post,
+    NullBooleanModel, BooleanModel, Document, IPLog)
 
 # If PIL available, do these tests.
 if Image:
@@ -224,6 +225,14 @@ class SlugFieldTests(test.TestCase):
         bs = BigS.objects.get(pk=bs.pk)
         self.assertEqual(bs.s, 'slug'*50)
 
+class IPFieldTests(test.TestCase):
+    def test_ip_empty(self):
+        """
+        Check it's possible to use empty values in IP field (#5622).
+        """
+        log_entry = IPLog.objects.create(ip="")
+        log_entry = IPLog.objects.get(pk=log_entry.pk)
+        self.assertEqual(log_entry.ip, None)
 
 class ValidationTest(test.TestCase):
     def test_charfield_raises_error_on_empty_string(self):