diff --git a/wagtail/api/v2/endpoints.py b/wagtail/api/v2/endpoints.py
index 04b6b74503..dacc62ed34 100644
--- a/wagtail/api/v2/endpoints.py
+++ b/wagtail/api/v2/endpoints.py
@@ -12,7 +12,7 @@ from rest_framework.response import Response
 from rest_framework.viewsets import GenericViewSet
 
 from wagtail.wagtailcore.models import Page
-from wagtail.wagtaildocs.models import Document
+from wagtail.wagtaildocs.models import get_document_model
 from wagtail.wagtailimages.models import get_image_model
 
 from .filters import (
@@ -282,4 +282,4 @@ class DocumentsAPIEndpoint(BaseAPIEndpoint):
     extra_meta_fields = ['tags', ]
     default_fields = ['title', 'tags']
     name = 'documents'
-    model = Document
+    model = get_document_model()
diff --git a/wagtail/api/v2/signal_handlers.py b/wagtail/api/v2/signal_handlers.py
index c57bc44ea8..c8e6c04165 100644
--- a/wagtail/api/v2/signal_handlers.py
+++ b/wagtail/api/v2/signal_handlers.py
@@ -6,7 +6,7 @@ from django.db.models.signals import post_delete, post_save
 from wagtail.contrib.wagtailfrontendcache.utils import purge_url_from_cache
 from wagtail.wagtailcore.models import get_page_models
 from wagtail.wagtailcore.signals import page_published, page_unpublished
-from wagtail.wagtaildocs.models import Document
+from wagtail.wagtaildocs.models import get_document_model
 from wagtail.wagtailimages.models import get_image_model
 
 from .utils import get_base_url
@@ -31,6 +31,7 @@ def purge_document_from_cache(instance, **kwargs):
 
 def register_signal_handlers():
     Image = get_image_model()
+    Document = get_document_model()
 
     for model in get_page_models():
         page_published.connect(purge_page_from_cache, sender=model)
@@ -44,6 +45,7 @@ def register_signal_handlers():
 
 def unregister_signal_handlers():
     Image = get_image_model()
+    Document = get_document_model()
 
     for model in get_page_models():
         page_published.disconnect(purge_page_from_cache, sender=model)
diff --git a/wagtail/contrib/wagtailapi/endpoints.py b/wagtail/contrib/wagtailapi/endpoints.py
index 5d0afa9b76..171679e6d9 100644
--- a/wagtail/contrib/wagtailapi/endpoints.py
+++ b/wagtail/contrib/wagtailapi/endpoints.py
@@ -12,7 +12,7 @@ from rest_framework.viewsets import GenericViewSet
 
 from wagtail.wagtailcore.models import Page
 from wagtail.wagtailcore.utils import resolve_model_string
-from wagtail.wagtaildocs.models import Document
+from wagtail.wagtaildocs.models import get_document_model
 from wagtail.wagtailimages.models import get_image_model
 
 from .filters import ChildOfFilter, DescendantOfFilter, FieldsFilter, OrderingFilter, SearchFilter
@@ -239,4 +239,4 @@ class DocumentsAPIEndpoint(BaseAPIEndpoint):
     filter_backends = [FieldsFilter, OrderingFilter, SearchFilter]
     extra_api_fields = ['title', 'tags']
     name = 'documents'
-    model = Document
+    model = get_document_model()
diff --git a/wagtail/contrib/wagtailapi/signal_handlers.py b/wagtail/contrib/wagtailapi/signal_handlers.py
index 4962bf2a2c..f3286edb0e 100644
--- a/wagtail/contrib/wagtailapi/signal_handlers.py
+++ b/wagtail/contrib/wagtailapi/signal_handlers.py
@@ -6,7 +6,7 @@ from django.db.models.signals import post_delete, post_save
 from wagtail.contrib.wagtailfrontendcache.utils import purge_url_from_cache
 from wagtail.wagtailcore.models import get_page_models
 from wagtail.wagtailcore.signals import page_published, page_unpublished
-from wagtail.wagtaildocs.models import Document
+from wagtail.wagtaildocs.models import get_document_model
 from wagtail.wagtailimages.models import get_image_model
 
 from .utils import get_base_url
@@ -31,6 +31,7 @@ def purge_document_from_cache(instance, **kwargs):
 
 def register_signal_handlers():
     Image = get_image_model()
+    Document = get_document_model()
 
     for model in get_page_models():
         page_published.connect(purge_page_from_cache, sender=model)
@@ -44,6 +45,7 @@ def register_signal_handlers():
 
 def unregister_signal_handlers():
     Image = get_image_model()
+    Document = get_document_model()
 
     for model in get_page_models():
         page_published.disconnect(purge_page_from_cache, sender=model)
diff --git a/wagtail/contrib/wagtailmedusa/renderers.py b/wagtail/contrib/wagtailmedusa/renderers.py
index 552b793e01..ba9e9495f5 100644
--- a/wagtail/contrib/wagtailmedusa/renderers.py
+++ b/wagtail/contrib/wagtailmedusa/renderers.py
@@ -2,7 +2,7 @@ from __future__ import absolute_import, unicode_literals
 
 from django_medusa.renderers import StaticSiteRenderer
 from wagtail.wagtailcore.models import Site
-from wagtail.wagtaildocs.models import Document
+from wagtail.wagtaildocs.models import get_document_model
 
 
 class PageRenderer(StaticSiteRenderer):
@@ -19,6 +19,8 @@ class PageRenderer(StaticSiteRenderer):
 
 class DocumentRenderer(StaticSiteRenderer):
     def get_paths(self):
+        Document = get_document_model()
+
         # Return list of paths to documents
         return (doc.url for doc in Document.objects.all())