diff --git a/wagtail/admin/apps.py b/wagtail/admin/apps.py
index 2732f8e6e7..e89deaa602 100644
--- a/wagtail/admin/apps.py
+++ b/wagtail/admin/apps.py
@@ -8,6 +8,7 @@ class WagtailAdminAppConfig(AppConfig):
     name = 'wagtail.admin'
     label = 'wagtailadmin'
     verbose_name = _("Wagtail admin")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         from wagtail.admin.signal_handlers import register_signal_handlers
diff --git a/wagtail/contrib/forms/apps.py b/wagtail/contrib/forms/apps.py
index df5cad6f86..78bdcf3859 100644
--- a/wagtail/contrib/forms/apps.py
+++ b/wagtail/contrib/forms/apps.py
@@ -6,3 +6,4 @@ class WagtailFormsAppConfig(AppConfig):
     name = 'wagtail.contrib.forms'
     label = 'wagtailforms'
     verbose_name = _("Wagtail forms")
+    default_auto_field = 'django.db.models.AutoField'
diff --git a/wagtail/contrib/redirects/apps.py b/wagtail/contrib/redirects/apps.py
index 9f0e55cfdf..d8e8080a54 100644
--- a/wagtail/contrib/redirects/apps.py
+++ b/wagtail/contrib/redirects/apps.py
@@ -6,3 +6,4 @@ class WagtailRedirectsAppConfig(AppConfig):
     name = 'wagtail.contrib.redirects'
     label = 'wagtailredirects'
     verbose_name = _("Wagtail redirects")
+    default_auto_field = 'django.db.models.AutoField'
diff --git a/wagtail/contrib/search_promotions/apps.py b/wagtail/contrib/search_promotions/apps.py
index 32daca5588..78f8cdca1c 100644
--- a/wagtail/contrib/search_promotions/apps.py
+++ b/wagtail/contrib/search_promotions/apps.py
@@ -6,3 +6,4 @@ class WagtailSearchPromotionsAppConfig(AppConfig):
     name = 'wagtail.contrib.search_promotions'
     label = 'wagtailsearchpromotions'
     verbose_name = _("Wagtail search promotions")
+    default_auto_field = 'django.db.models.AutoField'
diff --git a/wagtail/core/apps.py b/wagtail/core/apps.py
index b9321c652d..72bc59c30a 100644
--- a/wagtail/core/apps.py
+++ b/wagtail/core/apps.py
@@ -6,6 +6,7 @@ class WagtailCoreAppConfig(AppConfig):
     name = 'wagtail.core'
     label = 'wagtailcore'
     verbose_name = _("Wagtail core")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         from wagtail.core.signal_handlers import register_signal_handlers
diff --git a/wagtail/documents/apps.py b/wagtail/documents/apps.py
index 0b2532da4e..a9b7a961b6 100644
--- a/wagtail/documents/apps.py
+++ b/wagtail/documents/apps.py
@@ -6,6 +6,7 @@ class WagtailDocsAppConfig(AppConfig):
     name = 'wagtail.documents'
     label = 'wagtaildocs'
     verbose_name = _("Wagtail documents")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         from wagtail.documents.signal_handlers import register_signal_handlers
diff --git a/wagtail/embeds/apps.py b/wagtail/embeds/apps.py
index 51f0fd584e..eb70b28bce 100644
--- a/wagtail/embeds/apps.py
+++ b/wagtail/embeds/apps.py
@@ -8,6 +8,7 @@ class WagtailEmbedsAppConfig(AppConfig):
     name = 'wagtail.embeds'
     label = 'wagtailembeds'
     verbose_name = _("Wagtail embeds")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         # Check configuration on startup
diff --git a/wagtail/images/apps.py b/wagtail/images/apps.py
index f17cb248fe..bbfe0a3ed2 100644
--- a/wagtail/images/apps.py
+++ b/wagtail/images/apps.py
@@ -8,6 +8,7 @@ class WagtailImagesAppConfig(AppConfig):
     name = 'wagtail.images'
     label = 'wagtailimages'
     verbose_name = _("Wagtail images")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         from wagtail.images.signal_handlers import register_signal_handlers
diff --git a/wagtail/search/apps.py b/wagtail/search/apps.py
index 9a5fc2488e..547f3aee20 100644
--- a/wagtail/search/apps.py
+++ b/wagtail/search/apps.py
@@ -8,6 +8,7 @@ class WagtailSearchAppConfig(AppConfig):
     name = 'wagtail.search'
     label = 'wagtailsearch'
     verbose_name = _("Wagtail search")
+    default_auto_field = 'django.db.models.AutoField'
 
     def ready(self):
         register_signal_handlers()
diff --git a/wagtail/tests/demosite/__init__.py b/wagtail/tests/demosite/__init__.py
index e69de29bb2..7695f2c8ea 100644
--- a/wagtail/tests/demosite/__init__.py
+++ b/wagtail/tests/demosite/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'wagtail.tests.demosite.apps.DemositeAppConfig'
diff --git a/wagtail/tests/demosite/apps.py b/wagtail/tests/demosite/apps.py
new file mode 100644
index 0000000000..350ebce657
--- /dev/null
+++ b/wagtail/tests/demosite/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class DemositeAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
+    name = 'wagtail.tests.demosite'
diff --git a/wagtail/tests/i18n/__init__.py b/wagtail/tests/i18n/__init__.py
index e69de29bb2..af65a0eed7 100644
--- a/wagtail/tests/i18n/__init__.py
+++ b/wagtail/tests/i18n/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'wagtail.tests.i18n.apps.I18nAppConfig'
diff --git a/wagtail/tests/i18n/apps.py b/wagtail/tests/i18n/apps.py
new file mode 100644
index 0000000000..34b4352632
--- /dev/null
+++ b/wagtail/tests/i18n/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class I18nAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
+    name = 'wagtail.tests.i18n'
diff --git a/wagtail/tests/modeladmintest/apps.py b/wagtail/tests/modeladmintest/apps.py
index 947d5020ab..55d1b8df9c 100644
--- a/wagtail/tests/modeladmintest/apps.py
+++ b/wagtail/tests/modeladmintest/apps.py
@@ -3,6 +3,7 @@ from django.utils.translation import gettext_lazy as _
 
 
 class WagtailTestsAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'wagtail.tests.modeladmintest'
     label = 'modeladmintest'
     verbose_name = _("Test Wagtail Model Admin")
diff --git a/wagtail/tests/search/apps.py b/wagtail/tests/search/apps.py
index 753b7d5b96..7f285196cf 100644
--- a/wagtail/tests/search/apps.py
+++ b/wagtail/tests/search/apps.py
@@ -3,6 +3,7 @@ from django.utils.translation import gettext_lazy as _
 
 
 class WagtailSearchTestsAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'wagtail.tests.search'
     label = 'searchtests'
     verbose_name = _("Wagtail search tests")
diff --git a/wagtail/tests/snippets/apps.py b/wagtail/tests/snippets/apps.py
index 8827076db4..978f2c4256 100644
--- a/wagtail/tests/snippets/apps.py
+++ b/wagtail/tests/snippets/apps.py
@@ -3,6 +3,7 @@ from django.utils.translation import gettext_lazy as _
 
 
 class WagtailSnippetsTestsAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'wagtail.tests.snippets'
     label = 'snippetstests'
     verbose_name = _("Wagtail snippets tests")
diff --git a/wagtail/tests/testapp/apps.py b/wagtail/tests/testapp/apps.py
index 0a4b774b01..3f3d9b41f1 100644
--- a/wagtail/tests/testapp/apps.py
+++ b/wagtail/tests/testapp/apps.py
@@ -3,6 +3,7 @@ from django.utils.translation import gettext_lazy as _
 
 
 class WagtailTestsAppConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'wagtail.tests.testapp'
     label = 'tests'
     verbose_name = _("Wagtail tests")
diff --git a/wagtail/users/apps.py b/wagtail/users/apps.py
index 1d09daf170..d6afcc5ad0 100644
--- a/wagtail/users/apps.py
+++ b/wagtail/users/apps.py
@@ -6,3 +6,4 @@ class WagtailUsersAppConfig(AppConfig):
     name = 'wagtail.users'
     label = 'wagtailusers'
     verbose_name = _("Wagtail users")
+    default_auto_field = 'django.db.models.AutoField'