diff --git a/mayan/settings/base.py b/mayan/settings/base.py
index 4ce64295cb..f2f3888ac2 100644
--- a/mayan/settings/base.py
+++ b/mayan/settings/base.py
@@ -382,10 +382,10 @@ for app in INSTALLED_APPS:
         )
 
 
-for APP in COMMON_EXTRA_APPS:
+for APP in (COMMON_EXTRA_APPS or ()):
     INSTALLED_APPS = INSTALLED_APPS + (APP,)
 
 
 INSTALLED_APPS = [
-    APP for APP in INSTALLED_APPS if APP not in COMMON_DISABLED_APPS
+    APP for APP in INSTALLED_APPS if APP not in (COMMON_DISABLED_APPS or ())
 ]