diff --git a/configuration/ldap/ldap_config.py b/configuration/ldap/ldap_config.py
index 3071b45..f316ac0 100644
--- a/configuration/ldap/ldap_config.py
+++ b/configuration/ldap/ldap_config.py
@@ -77,7 +77,8 @@ if AUTH_LDAP_REQUIRE_GROUP is not None:
 
 # For more granular permissions, we can map LDAP groups to Django groups.
 AUTH_LDAP_FIND_GROUP_PERMS = environ.get('AUTH_LDAP_FIND_GROUP_PERMS', 'True').lower() == 'true'
-AUTH_LDAP_MIRROR_GROUPS = environ.get('AUTH_LDAP_MIRROR_GROUPS', '').lower() == 'true'
+if environ.get('AUTH_LDAP_MIRROR_GROUPS') is not None:
+    AUTH_LDAP_MIRROR_GROUPS = environ.get('AUTH_LDAP_MIRROR_GROUPS', '').lower() == 'true'
 
 # Cache groups for one hour to reduce LDAP traffic
 AUTH_LDAP_CACHE_TIMEOUT = int(environ.get('AUTH_LDAP_CACHE_TIMEOUT', 3600))