diff --git a/wagtail/wagtailsearch/tests/elasticsearch_common_tests.py b/wagtail/wagtailsearch/tests/elasticsearch_common_tests.py
index bb0c1a208..903cbb937 100644
--- a/wagtail/wagtailsearch/tests/elasticsearch_common_tests.py
+++ b/wagtail/wagtailsearch/tests/elasticsearch_common_tests.py
@@ -6,6 +6,7 @@ from io import StringIO
 from django.core import management
 
 from wagtail.tests.search import models
+from wagtail.wagtailsearch.query import MATCH_ALL
 
 
 class ElasticsearchCommonSearchBackendTests(object):
@@ -111,7 +112,7 @@ class ElasticsearchCommonSearchBackendTests(object):
         )
 
         # This should not give any results
-        results = self.backend.search(None, models.Book)
+        results = self.backend.search(MATCH_ALL, models.Book)
         self.assertSetEqual(set(results), set())
 
     def test_annotate_score(self):
@@ -129,7 +130,7 @@ class ElasticsearchCommonSearchBackendTests(object):
 
     def test_more_than_ten_results(self):
         # #3431 reported that Elasticsearch only sends back 10 results if the results set is not sliced
-        results = self.backend.search(None, models.Book)
+        results = self.backend.search(MATCH_ALL, models.Book)
 
         self.assertEqual(len(results), 13)
 
@@ -143,7 +144,7 @@ class ElasticsearchCommonSearchBackendTests(object):
         index.add_items(models.Book, books)
         index.refresh()
 
-        results = self.backend.search(None, models.Book)
+        results = self.backend.search(MATCH_ALL, models.Book)
         self.assertEqual(len(results), 163)
 
     def test_slice_more_than_one_hundred_results(self):
@@ -155,7 +156,7 @@ class ElasticsearchCommonSearchBackendTests(object):
         index.add_items(models.Book, books)
         index.refresh()
 
-        results = self.backend.search(None, models.Book)[10:120]
+        results = self.backend.search(MATCH_ALL, models.Book)[10:120]
         self.assertEqual(len(results), 110)
 
     def test_slice_to_next_page(self):
@@ -169,5 +170,5 @@ class ElasticsearchCommonSearchBackendTests(object):
         index.add_items(models.Book, books)
         index.refresh()
 
-        results = self.backend.search(None, models.Book)[110:]
+        results = self.backend.search(MATCH_ALL, models.Book)[110:]
         self.assertEqual(len(results), 53)
diff --git a/wagtail/wagtailsearch/tests/test_elasticsearch2_backend.py b/wagtail/wagtailsearch/tests/test_elasticsearch2_backend.py
index 1508e9a6e..4f1f853aa 100644
--- a/wagtail/wagtailsearch/tests/test_elasticsearch2_backend.py
+++ b/wagtail/wagtailsearch/tests/test_elasticsearch2_backend.py
@@ -13,6 +13,7 @@ from elasticsearch.serializer import JSONSerializer
 from wagtail.tests.search import models
 from wagtail.wagtailsearch.backends.elasticsearch2 import (
     Elasticsearch2SearchBackend, get_model_root)
+from wagtail.wagtailsearch.query import MATCH_ALL
 
 from .elasticsearch_common_tests import ElasticsearchCommonSearchBackendTests
 from .test_backends import BackendTests
@@ -57,9 +58,9 @@ class TestElasticsearch2SearchQuery(TestCase):
         }}
         self.assertDictEqual(query.get_query(), expected_result)
 
-    def test_none_query_string(self):
+    def test_match_all(self):
         # Create a query
-        query = self.query_class(models.Book.objects.all(), None)
+        query = self.query_class(models.Book.objects.all(), MATCH_ALL)
 
         # Check it
         expected_result = {'filtered': {
diff --git a/wagtail/wagtailsearch/tests/test_elasticsearch5_backend.py b/wagtail/wagtailsearch/tests/test_elasticsearch5_backend.py
index 8382a140a..1ad14a993 100644
--- a/wagtail/wagtailsearch/tests/test_elasticsearch5_backend.py
+++ b/wagtail/wagtailsearch/tests/test_elasticsearch5_backend.py
@@ -12,6 +12,7 @@ from elasticsearch.serializer import JSONSerializer
 
 from wagtail.tests.search import models
 from wagtail.wagtailsearch.backends.elasticsearch5 import Elasticsearch5SearchBackend
+from wagtail.wagtailsearch.query import MATCH_ALL
 
 from .elasticsearch_common_tests import ElasticsearchCommonSearchBackendTests
 from .test_backends import BackendTests
@@ -61,9 +62,9 @@ class TestElasticsearch5SearchQuery(TestCase):
         }}
         self.assertDictEqual(query.get_query(), expected_result)
 
-    def test_none_query_string(self):
+    def test_match_all(self):
         # Create a query
-        query = self.query_class(models.Book.objects.all(), None)
+        query = self.query_class(models.Book.objects.all(), MATCH_ALL)
 
         # Check it
         expected_result = {'bool': {