diff --git a/django/core/serializers/python.py b/django/core/serializers/python.py
index 0eeb485797..b672e4efc3 100644
--- a/django/core/serializers/python.py
+++ b/django/core/serializers/python.py
@@ -7,15 +7,15 @@ other serializers.
 from django.conf import settings
 from django.core.serializers import base
 from django.db import models
-from django.utils.encoding import smart_unicode
+from django.utils.encoding import smart_unicode, is_protected_type
 
 class Serializer(base.Serializer):
     """
     Serializes a QuerySet to basic Python objects.
     """
-    
+
     internal_use_only = True
-    
+
     def start_serialization(self):
         self._current = None
         self.objects = []
@@ -35,7 +35,14 @@ class Serializer(base.Serializer):
         self._current = None
 
     def handle_field(self, obj, field):
-        self._current[field.name] = smart_unicode(getattr(obj, field.name), strings_only=True)
+        value = field._get_val_from_obj(obj)
+        # Protected types (i.e., primitives like None, numbers, dates,
+        # and Decimals) are passed through as is. All other values are
+        # converted to string first.
+        if is_protected_type(value):
+            self._current[field.name] = value
+        else:
+            self._current[field.name] = field.value_to_string(obj)
 
     def handle_fk_field(self, obj, field):
         related = getattr(obj, field.name)
diff --git a/django/core/serializers/xml_serializer.py b/django/core/serializers/xml_serializer.py
index 04498db00c..2d74fe28f3 100644
--- a/django/core/serializers/xml_serializer.py
+++ b/django/core/serializers/xml_serializer.py
@@ -65,11 +65,9 @@ class Serializer(base.Serializer):
             "type" : field.get_internal_type()
         })
 
-        # Get a "string version" of the object's data (this is handled by the
-        # serializer base class).
+        # Get a "string version" of the object's data.
         if getattr(obj, field.name) is not None:
-            value = self.get_string_value(obj, field)
-            self.xml.characters(smart_unicode(value))
+            self.xml.characters(field.value_to_string(obj))
         else:
             self.xml.addQuickElement("None")
 
diff --git a/django/utils/encoding.py b/django/utils/encoding.py
index 7e87b05c79..9388d67f4c 100644
--- a/django/utils/encoding.py
+++ b/django/utils/encoding.py
@@ -41,6 +41,19 @@ def smart_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
         return s
     return force_unicode(s, encoding, strings_only, errors)
 
+def is_protected_type(obj):
+    """Determine if the object instance is of a protected type.
+
+    Objects of protected types are preserved as-is when passed to
+    force_unicode(strings_only=True).
+    """
+    return isinstance(obj, (
+        types.NoneType,
+        int, long,
+        datetime.datetime, datetime.date, datetime.time,
+        float, Decimal)
+    )
+
 def force_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
     """
     Similar to smart_unicode, except that lazy instances are resolved to
@@ -48,7 +61,7 @@ def force_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
 
     If strings_only is True, don't convert (some) non-string-like objects.
     """
-    if strings_only and isinstance(s, (types.NoneType, int, long, datetime.datetime, datetime.date, datetime.time, float, Decimal)):
+    if strings_only and is_protected_type(s):
         return s
     try:
         if not isinstance(s, basestring,):
diff --git a/tests/modeltests/serializers/models.py b/tests/modeltests/serializers/models.py
index eda19ecc4f..cf1bf50c24 100644
--- a/tests/modeltests/serializers/models.py
+++ b/tests/modeltests/serializers/models.py
@@ -73,6 +73,45 @@ class Movie(models.Model):
 class Score(models.Model):
     score = models.FloatField()
 
+
+class Team(object):
+    def __init__(self, title):
+        self.title = title
+
+    def __unicode__(self):
+        raise NotImplementedError("Not so simple")
+
+    def __str__(self):
+        raise NotImplementedError("Not so simple")
+
+    def to_string(self):
+        return "%s" % self.title
+
+class TeamField(models.CharField):
+    __metaclass__ = models.SubfieldBase
+
+    def __init__(self):
+        super(TeamField, self).__init__(max_length=100)
+
+    def get_db_prep_save(self, value):
+        return unicode(value.title)
+
+    def to_python(self, value):
+        if isinstance(value, Team):
+            return value
+        return Team(value)
+
+    def value_to_string(self, obj):
+        return self._get_val_from_obj(obj).to_string()
+
+class Player(models.Model):
+    name = models.CharField(max_length=50)
+    rank = models.IntegerField()
+    team = TeamField()
+
+    def __unicode__(self):
+        return u'%s (%d) playing for %s' % (self.name, self.rank, self.team.to_string())
+
 __test__ = {'API_TESTS':"""
 # Create some data:
 >>> from datetime import datetime
@@ -223,6 +262,21 @@ None
 >>> print list(serializers.deserialize('json', serializers.serialize('json', [sc])))[0].object.score
 3.4
 
+# Custom field with non trivial to string convertion value
+>>> player = Player()
+>>> player.name = "Soslan Djanaev"
+>>> player.rank = 1
+>>> player.team = Team("Spartak Moskva")
+>>> player.save()
+
+>>> serialized = serializers.serialize("json", Player.objects.all())
+>>> print serialized
+[{"pk": 1, "model": "serializers.player", "fields": {"name": "Soslan Djanaev", "rank": 1, "team": "Spartak Moskva"}}]
+
+>>> obj = list(serializers.deserialize("json", serialized))[0]
+>>> print obj
+<DeserializedObject: Soslan Djanaev (1) playing for Spartak Moskva>
+
 """}
 
 try:
@@ -259,6 +313,20 @@ try:
 <DeserializedObject: Just kidding; I love TV poker>
 <DeserializedObject: Time to reform copyright>
 
+# Custom field with non trivial to string convertion value with YAML serializer
+
+>>> print serializers.serialize("yaml", Player.objects.all())
+- fields: {name: Soslan Djanaev, rank: 1, team: Spartak Moskva}
+  model: serializers.player
+  pk: 1
+<BLANKLINE>
+
+>>> serialized = serializers.serialize("yaml", Player.objects.all())
+>>> obj = list(serializers.deserialize("yaml", serialized))[0]
+>>> print obj
+<DeserializedObject: Soslan Djanaev (1) playing for Spartak Moskva>
+
+
 """
 except ImportError:
     pass