diff --git a/api/__init__.py b/api/__init__.py
index 04ea581..ef866aa 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -7,7 +7,7 @@
 
 apiSpec = None  # API specification
 apiVersion = None  # API specification version. Extracted from the OpenAPI document.
-backendVersion = "1.3.12"  # Backend version number
+backendVersion = "1.3.13"  # Backend version number
 
 
 def _loadOpenApiSpec():
diff --git a/services/ldap.py b/services/ldap.py
index 8087614..8ba421c 100644
--- a/services/ldap.py
+++ b/services/ldap.py
@@ -60,10 +60,6 @@ def __init__(self, config=None):
         except Exception as err:
             msg = " - ".join(str(arg) for arg in err.args) or type(err).__name__
             raise ServiceUnavailableError("Failed to connect to server: "+msg)
-        if "filter" in self._config["users"]:
-            f = self._config["users"]["filter"]
-            if f is not None and len(f) != 0 and f[0] != "(" and f[-1] != ")":
-                self._config["users"]["filter"] = "("+f+")"
         if "defaultQuota" in self._config["users"]:
             self._defaultProps = {prop: self._config["users"]["defaultQuota"] for prop in
                                   ("storagequotalimit", "prohibitsendquota", "prohibitreceivequota")}
@@ -83,6 +79,10 @@ def _checkConfig(cls, config):
                 raise KeyError("Missing required config value '{}'".format(cls._configMap.get(required, "user."+required)))
         _templatesEnabled = config["users"].get("templates", [])
         userAttributes = {}
+        if "filter" in config["users"]:
+            f = config["users"]["filter"]
+            if f is not None and len(f) != 0 and f[0] != "(" and f[-1] != ")":
+                config["users"]["filter"] = "("+f+")"
         for _template in _templatesEnabled:
             if _template not in cls._templates:
                 raise ValueError("Unknown template '{}'".format(_template))
@@ -378,6 +378,7 @@ def searchUsers(self, query, domains=None, limit=25):
 
     @classmethod
     def testConfig(cls, config):
+        cls.init()
         try:
             cls._checkConfig(config)
             cls.testConnection(config)