diff --git a/HISTORY.rst b/HISTORY.rst
index eda4947749..d15056dffa 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -3,6 +3,7 @@
 * Fix an issue with some browsers not firing the .load event on cached
   images. Ref: http://api.jquery.com/load-event/
 * Remove duplicate YAML loading of environment variables.
+* Don't load development apps if they are already loaded.
 
 3.1.6 (2018-10-09)
 ==================
diff --git a/mayan/settings/development.py b/mayan/settings/development.py
index ea92f01268..41254180d1 100644
--- a/mayan/settings/development.py
+++ b/mayan/settings/development.py
@@ -9,10 +9,15 @@ DEBUG = True
 CELERY_ALWAYS_EAGER = True
 CELERY_EAGER_PROPAGATES_EXCEPTIONS = CELERY_ALWAYS_EAGER
 
-INSTALLED_APPS += (
-    'rosetta',
-    'django_extensions',
-)
+if 'rosetta' not in INSTALLED_APPS:
+    INSTALLED_APPS += (
+        'rosetta',
+    )
+
+if 'django_extensions' not in INSTALLED_APPS:
+    INSTALLED_APPS += (
+        'django_extensions',
+    )
 
 TEMPLATES[0]['OPTIONS']['loaders'] = (
     'django.template.loaders.filesystem.Loader',
diff --git a/mayan/settings/development_ddt.py b/mayan/settings/development_ddt.py
index f97a9add90..55dad05548 100644
--- a/mayan/settings/development_ddt.py
+++ b/mayan/settings/development_ddt.py
@@ -6,9 +6,10 @@ from .development import *  # NOQA
 # see https://github.com/django-debug-toolbar/django-debug-toolbar/issues/524
 DEBUG_TOOLBAR_PATCH_SETTINGS = False
 
-INSTALLED_APPS += (
-    'debug_toolbar',
-)
+if 'debug_toolbar' not in INSTALLED_APPS:
+    INSTALLED_APPS += (
+        'debug_toolbar',
+    )
 
 MIDDLEWARE_CLASSES = (
     'debug_toolbar.middleware.DebugToolbarMiddleware',