diff --git a/imagekit/models/fields/__init__.py b/imagekit/models/fields/__init__.py
index 04a6546..767374f 100644
--- a/imagekit/models/fields/__init__.py
+++ b/imagekit/models/fields/__init__.py
@@ -93,7 +93,7 @@ class ProcessedImageField(models.ImageField, SpecHostField):
 
     def __init__(self, processors=None, format=None, options=None,
             verbose_name=None, name=None, width_field=None, height_field=None,
-            autoconvert=True, spec=None, spec_id=None, **kwargs):
+            autoconvert=None, spec=None, spec_id=None, **kwargs):
         """
         The ProcessedImageField constructor accepts all of the arguments that
         the :class:`django.db.models.ImageField` constructor accepts, as well
@@ -101,6 +101,10 @@ class ProcessedImageField(models.ImageField, SpecHostField):
         :class:`imagekit.models.ImageSpecField`.
 
         """
+        # if spec is not provided then autoconvert will be True by default
+        if spec is None and autoconvert is None:
+            autoconvert = True
+
         SpecHost.__init__(self, processors=processors, format=format,
                 options=options, autoconvert=autoconvert, spec=spec,
                 spec_id=spec_id)
diff --git a/tests/models.py b/tests/models.py
index 5667cad..0f6bd0c 100644
--- a/tests/models.py
+++ b/tests/models.py
@@ -1,10 +1,17 @@
 from django.db import models
 
+from imagekit import ImageSpec
 from imagekit.models import ProcessedImageField
 from imagekit.models import ImageSpecField
 from imagekit.processors import Adjust, ResizeToFill, SmartCrop
 
 
+class Thumbnail(ImageSpec):
+    processors = [ResizeToFill(100, 60)]
+    format = 'JPEG'
+    options = {'quality': 60}
+
+
 class ImageModel(models.Model):
     image = models.ImageField(upload_to='b')
 
@@ -27,6 +34,10 @@ class ProcessedImageFieldModel(models.Model):
             options={'quality': 90}, upload_to='p')
 
 
+class ProcessedImageFieldWithSpecModel(models.Model):
+    processed = ProcessedImageField(spec=Thumbnail, upload_to='p')
+
+
 class CountingCacheFileStrategy(object):
     def __init__(self):
         self.on_existence_required_count = 0
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 6afb6cf..96e7337 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -5,7 +5,9 @@ from imagekit import forms as ikforms
 from imagekit.processors import SmartCrop
 from nose.tools import eq_
 from . import imagegenerators  # noqa
-from .models import ProcessedImageFieldModel, ImageModel
+from .models import (ProcessedImageFieldModel,
+                     ProcessedImageFieldWithSpecModel,
+                     ImageModel)
 from .utils import get_image_file
 
 
@@ -19,6 +21,16 @@ def test_model_processedimagefield():
     eq_(instance.processed.height, 50)
 
 
+def test_model_processedimagefield_with_spec():
+    instance = ProcessedImageFieldWithSpecModel()
+    file = File(get_image_file())
+    instance.processed.save('whatever.jpeg', file)
+    instance.save()
+
+    eq_(instance.processed.width, 100)
+    eq_(instance.processed.height, 60)
+
+
 def test_form_processedimagefield():
     class TestForm(forms.ModelForm):
         image = ikforms.ProcessedImageField(spec_id='tests:testform_image',