diff --git a/radicale-auth-ldap/__init__.py b/radicale-auth-ldap/__init__.py
index 7a6ec96..5065d9a 100644
--- a/radicale-auth-ldap/__init__.py
+++ b/radicale-auth-ldap/__init__.py
@@ -61,7 +61,7 @@ class Auth(BaseAuth):
             logger.warning("LDAP: binddn credentials are invalid")
             return ""
 
-        if accessGroupFilter:
+        if accessGroupFilter != None:
             logger.debug("LDAP access group filter: %s" % accessGroupFilter)
             logger.debug("LDAP access group attribute: %s" % accessGroupAttribute)
 
@@ -100,7 +100,7 @@ class Auth(BaseAuth):
                 userAttributeValue = conn.response[0]['attributes'][userAttribute]
                 logger.debug("LDAP user DN: %s" % userDn)
 
-                if accessGroupFilter:
+                if accessGroupFilter != None:
                     userMemberOf = conn.response[0]['attributes'][accessGroupAttribute]
 
                     userIsInAccessGroup = False