diff --git a/docs/changelog.rst b/docs/changelog.rst
index 8928d71..c68d02d 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,6 +1,12 @@
 Changelog
 ==========
 
+Version 0.5.3 (2013-09-17)
+--------------------------
+
+* Fix TypeError when ``base_form`` was not defined.
+
+
 Version 0.5.2 (2013-09-05)
 --------------------------
 
diff --git a/polymorphic/admin.py b/polymorphic/admin.py
index 019415b..454a522 100644
--- a/polymorphic/admin.py
+++ b/polymorphic/admin.py
@@ -400,8 +400,7 @@ class PolymorphicChildModelAdmin(admin.ModelAdmin):
         #
         # Instead, pass the form unchecked here, because the standard ModelForm will just work.
         # If the derived class sets the model explicitly, respect that setting.
-        if not self.form:
-            kwargs['form'] = self.base_form
+        kwargs.setdefault('form', self.base_form or self.form)
         return super(PolymorphicChildModelAdmin, self).get_form(request, obj, **kwargs)
 
 
@@ -479,11 +478,6 @@ class PolymorphicChildModelAdmin(admin.ModelAdmin):
             return self.base_fieldsets
 
 
-    def get_form(self, request, obj=None, **kwargs):
-        kwargs.setdefault('form', self.base_form)
-        return super(PolymorphicChildModelAdmin, self).get_form(request, obj, **kwargs)
-
-
     def get_subclass_fields(self, request, obj=None):
         # Find out how many fields would really be on the form,
         # if it weren't restricted by declared fields.
@@ -492,7 +486,7 @@ class PolymorphicChildModelAdmin(admin.ModelAdmin):
 
         # By not declaring the fields/form in the base class,
         # get_form() will populate the form with all available fields.
-        form = self.get_form(request, obj, exclude=exclude, form=self.base_form)
+        form = self.get_form(request, obj, exclude=exclude)
         subclass_fields = list(six.iterkeys(form.base_fields)) + list(self.get_readonly_fields(request, obj))
 
         # Find which fields are not part of the common fields.