diff --git a/django/contrib/admin/media/js/inlines.js b/django/contrib/admin/media/js/inlines.js
index 4e397b6..1f5933f 100644
--- a/django/contrib/admin/media/js/inlines.js
+++ b/django/contrib/admin/media/js/inlines.js
@@ -56,7 +56,7 @@
 				var template = $("#" + options.prefix + "-empty");
 				var row = template.clone(true).get(0);
 				$(row).removeClass(options.emptyCssClass).removeAttr("id").insertBefore($(template));
-				$(row).html($(row).html().replace(/__prefix__/g, nextIndex));
+				$(row).html($(row).html().replace(new RegExp(options.empty_form_prefix, "g"), nextIndex));
 				$(row).addClass(options.formCssClass).attr("id", options.prefix + nextIndex);
 				if ($(row).is("TR")) {
 					// If the forms are laid out in table rows, insert
@@ -118,6 +118,7 @@
 	/* Setup plugin defaults */
 	$.fn.formset.defaults = {
 		prefix: "form",					// The form prefix for your django formset
+		empty_form_prefix: "__prefix__",// The magic prefix bit on the empty form.
 		addText: "add another",			// Text for the add link
 		deleteText: "remove",			// Text for the delete link
 		addCssClass: "add-row",			// CSS class applied to the add link
diff --git a/django/contrib/admin/templates/admin/edit_inline/stacked.html b/django/contrib/admin/templates/admin/edit_inline/stacked.html
index fb112a0..81879d0 100644
--- a/django/contrib/admin/templates/admin/edit_inline/stacked.html
+++ b/django/contrib/admin/templates/admin/edit_inline/stacked.html
@@ -50,6 +50,7 @@
         }
         $(rows).formset({
             prefix: "{{ inline_admin_formset.formset.prefix }}",
+            empty_form_prefix: "{{ inline_admin_formset.formset.empty_form_prefix }}",
             addText: "{% blocktrans with inline_admin_formset.opts.verbose_name|title as verbose_name %}Add another {{ verbose_name }}{% endblocktrans %}",
             formCssClass: "dynamic-{{ inline_admin_formset.formset.prefix }}",
             deleteCssClass: "inline-deletelink",
diff --git a/django/contrib/admin/templates/admin/edit_inline/tabular.html b/django/contrib/admin/templates/admin/edit_inline/tabular.html
index dc9552f..d56944a 100644
--- a/django/contrib/admin/templates/admin/edit_inline/tabular.html
+++ b/django/contrib/admin/templates/admin/edit_inline/tabular.html
@@ -96,6 +96,7 @@
         }
         $(rows).formset({
             prefix: "{{ inline_admin_formset.formset.prefix }}",
+            empty_form_prefix: "{{ inline_admin_formset.formset.empty_form_prefix }}",
             addText: "{% blocktrans with inline_admin_formset.opts.verbose_name|title as verbose_name %}Add another {{ verbose_name }}{% endblocktrans %}",
             formCssClass: "dynamic-{{ inline_admin_formset.formset.prefix }}",
             deleteCssClass: "inline-deletelink",
diff --git a/django/forms/formsets.py b/django/forms/formsets.py
index ec14f81..03aa7ba 100644
--- a/django/forms/formsets.py
+++ b/django/forms/formsets.py
@@ -32,6 +32,8 @@ class BaseFormSet(StrAndUnicode):
     """
     A collection of instances of the same Form class.
     """
+    empty_form_prefix = '__prefix__'
+
     def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                  initial=None, error_class=ErrorList):
         self.is_bound = data is not None or files is not None
@@ -125,7 +127,7 @@ class BaseFormSet(StrAndUnicode):
     def _get_empty_form(self, **kwargs):
         defaults = {
             'auto_id': self.auto_id,
-            'prefix': self.add_prefix('__prefix__'),
+            'prefix': self.add_prefix(self.empty_form_prefix),
             'empty_permitted': True,
         }
         if self.data or self.files:
diff --git a/tests/regressiontests/forms/formsets.py b/tests/regressiontests/forms/formsets.py
index 3eecb7f..6c9bf01 100644
--- a/tests/regressiontests/forms/formsets.py
+++ b/tests/regressiontests/forms/formsets.py
@@ -1,4 +1,19 @@
 # -*- coding: utf-8 -*-
+
+from django import forms
+from django.forms.formsets import formset_factory
+from django.test import TestCase
+
+class EmptyFormTestCase(TestCase):
+    def test_custom_empty_form_prefix(self):
+        class BasicForm(forms.Form):
+            value = forms.CharField()
+        
+        FormSet = formset_factory(BasicForm)
+        FormSet.empty_form_prefix = "__pony__"
+        self.assertEqual(str(FormSet().empty_form), """<tr><th><label for="id_form-__pony__-value">Value:</label></th><td><input type="text" name="form-__pony__-value" id="id_form-__pony__-value" /></td></tr>""")
+
+
 tests = """
 # Basic FormSet creation and usage ############################################
 
diff --git a/tests/regressiontests/forms/tests.py b/tests/regressiontests/forms/tests.py
index 8757e79..e50a10f 100644
--- a/tests/regressiontests/forms/tests.py
+++ b/tests/regressiontests/forms/tests.py
@@ -34,7 +34,7 @@ from localflavor.za import tests as localflavor_za_tests
 from regressions import tests as regression_tests
 from util import tests as util_tests
 from widgets import tests as widgets_tests
-from formsets import tests as formset_tests
+from formsets import tests as formset_tests, EmptyFormTestCase
 from media import media_tests
 
 from fields import FieldsTests