diff --git a/mayan/apps/acls/apps.py b/mayan/apps/acls/apps.py
index 5f79f0fc0e..f46839f3cc 100644
--- a/mayan/apps/acls/apps.py
+++ b/mayan/apps/acls/apps.py
@@ -6,7 +6,6 @@ from common import MayanAppConfig, menu_object, menu_sidebar
 from navigation import SourceColumn
 
 from .links import link_acl_new, link_acl_delete, link_acl_permissions
-from .models import AccessControlList
 
 
 class ACLsApp(MayanAppConfig):
@@ -17,6 +16,8 @@ class ACLsApp(MayanAppConfig):
     def ready(self):
         super(ACLsApp, self).ready()
 
+        AccessControlList = self.get_model('AccessControlList')
+
         SourceColumn(
             source=AccessControlList, label=_('Permissions'),
             attribute='get_permission_titles'
diff --git a/mayan/apps/checkouts/apps.py b/mayan/apps/checkouts/apps.py
index 76f8f12e88..660dce0b1c 100644
--- a/mayan/apps/checkouts/apps.py
+++ b/mayan/apps/checkouts/apps.py
@@ -17,7 +17,6 @@ from .links import (
     link_checkout_list
 )
 from .literals import CHECK_EXPIRED_CHECK_OUTS_INTERVAL
-from .models import DocumentCheckout
 from .permissions import (
     permission_document_checkin, permission_document_checkin_override,
     permission_document_checkout
@@ -36,6 +35,8 @@ class CheckoutsApp(MayanAppConfig):
 
         APIEndPoint(app=self, version_string='1')
 
+        DocumentCheckout = self.get_model('DocumentCheckout')
+
         Document.add_to_class(
             'check_in',
             lambda document, user=None: DocumentCheckout.objects.check_in_document(document, user)
diff --git a/mayan/apps/converter/apps.py b/mayan/apps/converter/apps.py
index 727967327b..f2527f9b50 100644
--- a/mayan/apps/converter/apps.py
+++ b/mayan/apps/converter/apps.py
@@ -11,7 +11,6 @@ from .links import (
     link_transformation_create, link_transformation_delete,
     link_transformation_edit
 )
-from .models import Transformation
 
 
 class ConverterApp(MayanAppConfig):
@@ -21,6 +20,8 @@ class ConverterApp(MayanAppConfig):
     def ready(self):
         super(ConverterApp, self).ready()
 
+        Transformation = self.get_model('Transformation')
+
         Package(label='Pillow', license_text='''
 The Python Imaging Library (PIL) is
 
diff --git a/mayan/apps/document_comments/apps.py b/mayan/apps/document_comments/apps.py
index 378ed7f66e..5b52b73d98 100644
--- a/mayan/apps/document_comments/apps.py
+++ b/mayan/apps/document_comments/apps.py
@@ -10,7 +10,6 @@ from navigation import SourceColumn
 from .links import (
     link_comment_add, link_comment_delete, link_comments_for_document
 )
-from .models import Comment
 from .permissions import (
     permission_comment_create, permission_comment_delete,
     permission_comment_view
@@ -26,6 +25,8 @@ class DocumentCommentsApp(MayanAppConfig):
     def ready(self):
         super(DocumentCommentsApp, self).ready()
 
+        Comment = self.get_model('Comment')
+
         ModelPermission.register(
             model=Document, permissions=(
                 permission_comment_create, permission_comment_delete,
diff --git a/mayan/apps/document_indexing/apps.py b/mayan/apps/document_indexing/apps.py
index a90d51381a..6dc211800a 100644
--- a/mayan/apps/document_indexing/apps.py
+++ b/mayan/apps/document_indexing/apps.py
@@ -30,10 +30,6 @@ from .links import (
     link_template_node_create, link_template_node_delete,
     link_template_node_edit
 )
-from .models import (
-    DocumentIndexInstanceNode, Index, IndexInstance, IndexInstanceNode,
-    IndexTemplateNode
-)
 from .widgets import get_breadcrumbs, index_instance_item_link, node_level
 
 
@@ -47,6 +43,12 @@ class DocumentIndexingApp(MayanAppConfig):
     def ready(self):
         super(DocumentIndexingApp, self).ready()
 
+        DocumentIndexInstanceNode = self.get_model('DocumentIndexInstanceNode')
+        Index = self.get_model('Index')
+        IndexInstance = self.get_model('IndexInstance')
+        IndexInstanceNode = self.get_model('IndexInstanceNode')
+        IndexTemplateNode = self.get_model('IndexTemplateNode')
+
         APIEndPoint(app=self, version_string='1')
 
         Package(label='Django MPTT', license_text='''
diff --git a/mayan/apps/document_signatures/apps.py b/mayan/apps/document_signatures/apps.py
index 592181aaf8..69dc4a245b 100644
--- a/mayan/apps/document_signatures/apps.py
+++ b/mayan/apps/document_signatures/apps.py
@@ -11,11 +11,11 @@ from django_gpg.exceptions import GPGDecryptionError
 from django_gpg.runtime import gpg
 from documents.models import Document, DocumentVersion
 
+from .hooks import document_pre_open_hook, document_version_post_save_hook
 from .links import (
     link_document_signature_delete, link_document_signature_download,
     link_document_signature_upload, link_document_verify
 )
-from .models import DocumentVersionSignature
 from .permissions import (
     permission_document_verify, permission_signature_delete,
     permission_signature_download, permission_signature_upload
@@ -24,37 +24,6 @@ from .permissions import (
 logger = logging.getLogger(__name__)
 
 
-def document_pre_open_hook(descriptor, instance):
-    if DocumentVersionSignature.objects.has_embedded_signature(document_version=instance):
-        # If it has an embedded signature, decrypt
-        try:
-            result = gpg.decrypt_file(descriptor, close_descriptor=False)
-            # gpg return a string, turn it into a file like object
-        except GPGDecryptionError:
-            # At least return the original raw content
-            descriptor.seek(0)
-            return descriptor
-        else:
-            descriptor.close()
-            return io.BytesIO(result.data)
-    else:
-        return descriptor
-
-
-def document_version_post_save_hook(instance):
-    logger.debug('instance: %s', instance)
-
-    try:
-        document_signature = DocumentVersionSignature.objects.get(
-            document_version=instance
-        )
-    except DocumentVersionSignature.DoesNotExist:
-        document_signature = DocumentVersionSignature.objects.create(
-            document_version=instance
-        )
-        document_signature.check_for_embedded_signature()
-
-
 class DocumentSignaturesApp(MayanAppConfig):
     app_namespace = 'signatures'
     app_url = 'signatures'
@@ -65,6 +34,8 @@ class DocumentSignaturesApp(MayanAppConfig):
     def ready(self):
         super(DocumentSignaturesApp, self).ready()
 
+        DocumentVersionSignature = self.get_model('DocumentVersionSignature')
+
         DocumentVersion.register_post_save_hook(
             1, document_version_post_save_hook
         )
diff --git a/mayan/apps/document_states/apps.py b/mayan/apps/document_states/apps.py
index d93e79bb03..0af6eb8132 100644
--- a/mayan/apps/document_states/apps.py
+++ b/mayan/apps/document_states/apps.py
@@ -12,10 +12,6 @@ from documents.models import Document
 from navigation import SourceColumn
 
 from .handlers import launch_workflow
-from .models import (
-    Workflow, WorkflowInstance, WorkflowInstanceLogEntry, WorkflowState,
-    WorkflowTransition
-)
 from .links import (
     link_document_workflow_instance_list, link_setup_workflow_document_types,
     link_setup_workflow_create, link_setup_workflow_delete,
@@ -37,6 +33,12 @@ class DocumentStatesApp(MayanAppConfig):
     def ready(self):
         super(DocumentStatesApp, self).ready()
 
+        Workflow = self.get_model('Workflow')
+        WorkflowInstance = self.get_model('WorkflowInstance')
+        WorkflowInstanceLogEntry = self.get_model('WorkflowInstanceLogEntry')
+        WorkflowState = self.get_model('WorkflowState')
+        WorkflowTransition = self.get_model('WorkflowTransition')
+
         SourceColumn(
             source=Workflow, label=_('Initial state'),
             func=lambda context: context['object'].get_initial_state() or _('None')
diff --git a/mayan/apps/documents/apps.py b/mayan/apps/documents/apps.py
index 344529af39..9927703d8c 100644
--- a/mayan/apps/documents/apps.py
+++ b/mayan/apps/documents/apps.py
@@ -60,10 +60,6 @@ from .literals import (
     CHECK_DELETE_PERIOD_INTERVAL, CHECK_TRASH_PERIOD_INTERVAL,
     DELETE_STALE_STUBS_INTERVAL
 )
-from .models import (
-    DeletedDocument, Document, DocumentPage, DocumentType,
-    DocumentTypeFilename, DocumentVersion
-)
 from .permissions import (
     permission_document_delete, permission_document_download,
     permission_document_edit, permission_document_new_version,
@@ -90,6 +86,13 @@ class DocumentsApp(MayanAppConfig):
 
         APIEndPoint(app=self, version_string='1')
 
+        DeletedDocument = self.get_model('DeletedDocument')
+        Document = self.get_model('Document')
+        DocumentPage = self.get_model('DocumentPage')
+        DocumentType = self.get_model('DocumentType')
+        DocumentTypeFilename = self.get_model('DocumentTypeFilename')
+        DocumentVersion = self.get_model('DocumentVersion')
+
         MissingItem(
             label=_('Create a document type'),
             description=_(
diff --git a/mayan/apps/folders/apps.py b/mayan/apps/folders/apps.py
index 6926e0cded..467949f6d5 100644
--- a/mayan/apps/folders/apps.py
+++ b/mayan/apps/folders/apps.py
@@ -20,7 +20,6 @@ from .links import (
     link_folder_delete, link_folder_document_multiple_remove,
     link_folder_edit, link_folder_view
 )
-from .models import DocumentFolder, Folder
 from .permissions import (
     permission_folder_add_document, permission_folder_delete,
     permission_folder_edit, permission_folder_remove_document,
@@ -36,6 +35,9 @@ class FoldersApp(MayanAppConfig):
     def ready(self):
         super(FoldersApp, self).ready()
 
+        DocumentFolder = self.get_model('DocumentFolder')
+        Folder = self.get_model('Folder')
+
         APIEndPoint(app=self, version_string='1')
 
         Document.add_to_class(
diff --git a/mayan/apps/linking/apps.py b/mayan/apps/linking/apps.py
index 7643a1e52d..8a0ac798ff 100644
--- a/mayan/apps/linking/apps.py
+++ b/mayan/apps/linking/apps.py
@@ -21,7 +21,6 @@ from .links import (
     link_smart_link_instance_view, link_smart_link_instances_for_document,
     link_smart_link_list, link_smart_link_setup
 )
-from .models import ResolvedSmartLink, SmartLink, SmartLinkCondition
 from .permissions import (
     permission_smart_link_delete, permission_smart_link_edit,
     permission_smart_link_view
@@ -35,6 +34,10 @@ class LinkingApp(MayanAppConfig):
     def ready(self):
         super(LinkingApp, self).ready()
 
+        ResolvedSmartLink = self.get_model('ResolvedSmartLink')
+        SmartLink = self.get_model('SmartLink')
+        SmartLinkCondition = self.get_model('SmartLinkCondition')
+
         ModelPermission.register(
             model=SmartLink, permissions=(
                 permission_acl_edit, permission_acl_view,
diff --git a/mayan/apps/mailer/apps.py b/mayan/apps/mailer/apps.py
index 158788e176..b7eefbb8f7 100644
--- a/mayan/apps/mailer/apps.py
+++ b/mayan/apps/mailer/apps.py
@@ -14,7 +14,6 @@ from .links import (
     link_document_mailing_error_log, link_send_document_link,
     link_send_document
 )
-from .models import LogEntry
 from .permissions import (
     permission_mailing_link, permission_mailing_send_document
 )
@@ -27,6 +26,8 @@ class MailerApp(MayanAppConfig):
     def ready(self):
         super(MailerApp, self).ready()
 
+        LogEntry = self.get_model('LogEntry')
+
         SourceColumn(
             source=LogEntry, label=_('Date and time'), attribute='datetime'
         )
diff --git a/mayan/apps/metadata/apps.py b/mayan/apps/metadata/apps.py
index cf521bbd05..79281600c8 100644
--- a/mayan/apps/metadata/apps.py
+++ b/mayan/apps/metadata/apps.py
@@ -37,7 +37,6 @@ from .links import (
     link_setup_metadata_type_create, link_setup_metadata_type_delete,
     link_setup_metadata_type_edit, link_setup_metadata_type_list,
 )
-from .models import DocumentMetadata, DocumentTypeMetadataType, MetadataType
 from .permissions import (
     permission_metadata_document_add, permission_metadata_document_edit,
     permission_metadata_document_remove, permission_metadata_document_view
@@ -55,6 +54,10 @@ class MetadataApp(MayanAppConfig):
     def ready(self):
         super(MetadataApp, self).ready()
 
+        DocumentMetadata = self.get_model('DocumentMetadata')
+        DocumentTypeMetadataType = self.get_model('DocumentTypeMetadataType')
+        MetadataType = self.get_model('MetadataType')
+
         APIEndPoint(app=self, version_string='1')
 
         Document.add_to_class(
diff --git a/mayan/apps/ocr/apps.py b/mayan/apps/ocr/apps.py
index 7a57d36f3a..2b8afff5b9 100644
--- a/mayan/apps/ocr/apps.py
+++ b/mayan/apps/ocr/apps.py
@@ -29,7 +29,6 @@ from .links import (
     link_document_submit_multiple, link_document_type_ocr_settings,
     link_document_type_submit, link_entry_list
 )
-from .models import DocumentVersionOCRError
 from .permissions import permission_ocr_document, permission_ocr_content_view
 from .settings import (
     setting_pdftotext_path, setting_tesseract_path
@@ -58,6 +57,8 @@ class OCRApp(MayanAppConfig):
     def ready(self):
         super(OCRApp, self).ready()
 
+        DocumentVersionOCRError = self.get_model('DocumentVersionOCRError')
+
         APIEndPoint(app=self, version_string='1')
 
         Document.add_to_class('submit_for_ocr', document_ocr_submit)
diff --git a/mayan/apps/permissions/apps.py b/mayan/apps/permissions/apps.py
index d2fa84dd01..9cc06178c1 100644
--- a/mayan/apps/permissions/apps.py
+++ b/mayan/apps/permissions/apps.py
@@ -9,7 +9,6 @@ from common.signals import perform_upgrade
 from rest_api.classes import APIEndPoint
 
 from .handlers import purge_permissions
-from .models import Role
 from .links import (
     link_permission_grant, link_permission_revoke, link_role_create,
     link_role_delete, link_role_edit, link_role_list, link_role_members,
@@ -25,6 +24,8 @@ class PermissionsApp(MayanAppConfig):
     def ready(self):
         super(PermissionsApp, self).ready()
 
+        Role = self.get_model('Role')
+
         APIEndPoint(app=self, version_string='1')
 
         menu_object.bind_links(
diff --git a/mayan/apps/sources/apps.py b/mayan/apps/sources/apps.py
index 1e96231734..cc4230d710 100644
--- a/mayan/apps/sources/apps.py
+++ b/mayan/apps/sources/apps.py
@@ -30,10 +30,6 @@ from .links import (
     link_setup_source_edit, link_setup_source_logs, link_staging_file_delete,
     link_upload_version
 )
-from .models import (
-    POP3Email, IMAPEmail, Source, SourceLog, StagingFolderSource,
-    WatchFolderSource, WebFormSource
-)
 from .widgets import staging_file_thumbnail
 
 
@@ -45,6 +41,14 @@ class SourcesApp(MayanAppConfig):
     def ready(self):
         super(SourcesApp, self).ready()
 
+        POP3Email = self.get_model('POP3Email')
+        IMAPEmail = self.get_model('IMAPEmail')
+        Source = self.get_model('Source')
+        SourceLog = self.get_model('SourceLog')
+        StagingFolderSource = self.get_model('StagingFolderSource')
+        WatchFolderSource = self.get_model('WatchFolderSource')
+        WebFormSource = self.get_model('WebFormSource')
+
         APIEndPoint(app=self, version_string='1')
 
         MissingItem(
diff --git a/mayan/apps/tags/apps.py b/mayan/apps/tags/apps.py
index c6f230b3a7..df13311c11 100644
--- a/mayan/apps/tags/apps.py
+++ b/mayan/apps/tags/apps.py
@@ -20,7 +20,6 @@ from .links import (
     link_tag_delete, link_tag_document_list, link_tag_edit, link_tag_list,
     link_tag_multiple_delete, link_tag_tagged_item_list
 )
-from .models import DocumentTag, Tag
 from .permissions import (
     permission_tag_attach, permission_tag_delete, permission_tag_edit,
     permission_tag_remove, permission_tag_view
@@ -36,6 +35,9 @@ class TagsApp(MayanAppConfig):
     def ready(self):
         super(TagsApp, self).ready()
 
+        DocumentTag = self.get_model('DocumentTag')
+        Tag = self.get_model('Tag')
+
         APIEndPoint(app=self, version_string='1')
 
         Document.add_to_class(