diff --git a/url_filter/filtersets/plain.py b/url_filter/filtersets/plain.py
index c6b74a2..b502f2f 100644
--- a/url_filter/filtersets/plain.py
+++ b/url_filter/filtersets/plain.py
@@ -6,6 +6,7 @@
 import six
 from django import forms
 
+from ..backends.plain import PlainFilterBackend
 from ..exceptions import SkipFilter
 from ..filters import Filter
 from ..utils import SubClassDict, dictify
@@ -31,6 +32,7 @@ class PlainModelFilterSet(BaseModelFilterSet):
     The filterset can be configured via ``Meta`` class attribute,
     very much like Django's ``ModelForm`` is configured.
     """
+    filter_backend_class = PlainFilterBackend
 
     def _build_state(self):
         return dictify(self.Meta.model)
diff --git a/url_filter/filtersets/sqlalchemy.py b/url_filter/filtersets/sqlalchemy.py
index f0e47fa..63eb27b 100644
--- a/url_filter/filtersets/sqlalchemy.py
+++ b/url_filter/filtersets/sqlalchemy.py
@@ -67,6 +67,7 @@ class SQLAlchemyModelFilterSet(BaseModelFilterSet):
     The filterset can be configured via ``Meta`` class attribute,
     very much like Django's ``ModelForm`` is configured.
     """
+    filter_backend_class = SQLAlchemyFilterBackend
 
     def _build_filter(self, name, fields):
         field = fields[name]