diff --git a/formtools/utils.py b/formtools/utils.py
index 8bfebfb..d7b408e 100644
--- a/formtools/utils.py
+++ b/formtools/utils.py
@@ -1,8 +1,29 @@
 import pickle
 
+from django.db.models import QuerySet
 from django.utils.crypto import salted_hmac
 
 
+def sanitise(obj):
+    if type(obj) == list:
+        return [sanitise(o) for o in obj]
+    elif type(obj) == tuple:
+        return tuple([sanitise(o) for o in obj])
+    elif type(obj) == QuerySet:
+        return [sanitise(o) for o in list(obj)]
+    try:
+        od = obj.__dict__
+        nd = {'_class': obj.__class__}
+        for key, val in od.items():
+            if not key.startswith('_'):
+                # ignore Django internal attributes
+                nd[key] = sanitise(val)
+        return nd
+    except Exception:
+        pass
+    return obj
+
+
 def form_hmac(form):
     """
     Calculates a security hash for the given Form instance.
@@ -19,6 +40,7 @@ def form_hmac(form):
             value = value.strip()
         data.append((bf.name, value))
 
-    pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
+    sanitised_data = sanitise(data)
+    pickled = pickle.dumps(sanitised_data, pickle.HIGHEST_PROTOCOL)
     key_salt = 'django.contrib.formtools'
     return salted_hmac(key_salt, pickled).hexdigest()
diff --git a/tests/forms.py b/tests/forms.py
index 3542978..65c3cdb 100644
--- a/tests/forms.py
+++ b/tests/forms.py
@@ -1,4 +1,26 @@
 from django import forms
+from django.db import models
+
+
+class ManyModel(models.Model):
+    name = models.CharField(max_length=100)
+
+    class Meta:
+        app_label = 'formtools'
+
+
+class OtherModel(models.Model):
+    name = models.CharField(max_length=100)
+    manymodels = models.ManyToManyField(ManyModel)
+
+    class Meta:
+        app_label = 'formtools'
+
+
+class OtherModelForm(forms.ModelForm):
+    class Meta:
+        model = OtherModel
+        fields = '__all__'
 
 
 class TestForm(forms.Form):
diff --git a/tests/tests.py b/tests/tests.py
index a2f0778..eeaf98d 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -8,7 +8,9 @@
 
 from formtools import preview, utils
 
-from .forms import HashTestBlankForm, HashTestForm, TestForm
+from .forms import (
+    HashTestBlankForm, HashTestForm, ManyModel, OtherModelForm, TestForm,
+)
 
 success_string = "Done was called!"
 success_string_encoded = success_string.encode()
@@ -191,3 +193,28 @@ def test_empty_permitted(self):
         hash1 = utils.form_hmac(f1)
         hash2 = utils.form_hmac(f2)
         self.assertEqual(hash1, hash2)
+
+
+class PicklingTests(unittest.TestCase):
+
+    def setUp(self):
+        super(PicklingTests, self).setUp()
+        ManyModel.objects.create(name="jane")
+
+    def test_queryset_hash(self):
+        """
+        Regression test for #10034: the hash generation function should ignore
+        leading/trailing whitespace so as to be friendly to broken browsers that
+        submit it (usually in textareas).
+        """
+
+        qs1 = ManyModel.objects.all()
+        qs2 = ManyModel.objects.all()
+
+        qs1._prefetch_done = True
+        qs2._prefetch_done = False
+        f1 = OtherModelForm({'name': 'joe', 'manymodels': qs1})
+        f2 = OtherModelForm({'name': 'joe', 'manymodels': qs2})
+        hash1 = utils.form_hmac(f1)
+        hash2 = utils.form_hmac(f2)
+        self.assertEqual(hash1, hash2)