diff --git a/management/univention-management-console-module-udm/umc/python/udm/__init__.py b/management/univention-management-console-module-udm/umc/python/udm/__init__.py
index c70ee92..a2e47ba 100644
--- a/management/univention-management-console-module-udm/umc/python/udm/__init__.py
+++ b/management/univention-management-console-module-udm/umc/python/udm/__init__.py
@@ -69,7 +69,7 @@
 
 from .udm_ldap import (
 	UDM_Error, UDM_Module, UDM_Settings,
-	ldap_dn2path, get_module, read_syntax_choices, list_objects,
+	ldap_dn2path, get_module, read_syntax_choices, list_objects, _get_syntax,
 	LDAP_Connection, set_bind_function, container_modules,
 	info_syntax_choices, search_syntax_choices_by_key,
 	UserWithoutDN, ObjectDoesNotExist, SuperordinateDoesNotExist, NoIpLeft,
@@ -894,13 +894,23 @@ def _thread(request):
 		thread = notifier.threads.Simple('Validate', notifier.Callback(_thread, request), notifier.Callback(self.thread_finished_callback, request))
 		thread.run()
 
-	@sanitize(key=LDAPSearchSanitizer(use_asterisks=False))
+	@sanitize(
+		syntax=StringSanitizer(required=True),
+		key=LDAPSearchSanitizer(use_asterisks=False),
+	)
 	@simple_response
 	def syntax_choices_key(self, syntax, key):
+		syntax = _get_syntax(syntax)
+		if syntax is None:
+			return
 		return search_syntax_choices_by_key(syntax, key)
 
+	@sanitize(syntax=StringSanitizer(required=True))
 	@simple_response
 	def syntax_choices_info(self, syntax):
+		syntax = _get_syntax(syntax)
+		if syntax is None:
+			return
 		return info_syntax_choices(syntax)
 
 	@sanitize(
@@ -918,7 +928,10 @@ def syntax_choices(self, request):
 		"""
 
 		def _thread(request):
-			return read_syntax_choices(request.options['syntax'], request.options)
+			syntax = _get_syntax(request.options['syntax'])
+			if syntax is None:
+				return
+			return read_syntax_choices(syntax, request.options)
 
 		thread = notifier.threads.Simple('SyntaxChoice', notifier.Callback(_thread, request), notifier.Callback(self.thread_finished_callback, request))
 		thread.run()
diff --git a/management/univention-management-console-module-udm/umc/python/udm/udm_ldap.py b/management/univention-management-console-module-udm/umc/python/udm/udm_ldap.py
index 0dbed9a..9ebe573 100644
--- a/management/univention-management-console-module-udm/umc/python/udm/udm_ldap.py
+++ b/management/univention-management-console-module-udm/umc/python/udm/udm_ldap.py
@@ -275,7 +275,7 @@ def get_default_values(self, property_name):
 			if key == property_name:
 				value = default_value(prop.syntax)
 				if isinstance(value, (list, tuple)):
-					value = read_syntax_choices(prop.syntax.name)
+					value = read_syntax_choices(prop.syntax)
 				return value
 
 	def _map_properties(self, obj, properties):
@@ -1126,16 +1126,12 @@ def _get_syntax(syntax_name):
 	return udm_syntax.__dict__[syntax_name]()
 
 
-def search_syntax_choices_by_key(syntax_name, key):
-	syn = _get_syntax(syntax_name)
-	if syn is None:
-		return None
-
+def search_syntax_choices_by_key(syn, key):
 	if issubclass(syn.__class__, udm_syntax.UDM_Objects):
 		if syn.key == 'dn':
 			module_search_options = {'scope': 'base', 'container': key}
 			try:
-				return read_syntax_choices(syntax_name, {}, module_search_options)
+				return read_syntax_choices(syn, {}, module_search_options)
 			except udm_errors.base:  # TODO: which exception is raised here exactly?
 				# invalid DN
 				return []
@@ -1144,19 +1140,15 @@ def search_syntax_choices_by_key(syntax_name, key):
 			if match:
 				attr = match.groups()[0]
 				options = {'objectProperty': attr, 'objectPropertyValue': key}
-				return read_syntax_choices(syntax_name, options)
+				return read_syntax_choices(syn, options)
 
-	MODULE.warn('Syntax "%s": No fast search function' % syntax_name)
+	MODULE.warn('Syntax %r: No fast search function' % syn.name)
 	# return them all, as there is no reason to filter after everything has loaded
 	# frontend will cache it.
-	return read_syntax_choices(syntax_name)
-
+	return read_syntax_choices(syn)
 
-def info_syntax_choices(syntax_name, options={}):
-	syn = _get_syntax(syntax_name)
-	if syn is None:
-		return None
 
+def info_syntax_choices(syn, options={}):
 	if issubclass(syn.__class__, udm_syntax.UDM_Objects):
 		size = 0
 		if syn.static_values is not None:
@@ -1176,10 +1168,8 @@ def info_syntax_choices(syntax_name, options={}):
 
 
 @LDAP_Connection
-def read_syntax_choices(syntax_name, options={}, module_search_options={}, ldap_connection=None, ldap_position=None):
-	syn = _get_syntax(syntax_name)
-	if syn is None:
-		return None
+def read_syntax_choices(syn, options={}, module_search_options={}, ldap_connection=None, ldap_position=None):
+	syntax_name = syn.name
 
 	if issubclass(syn.__class__, udm_syntax.UDM_Objects):
 		syn.choices = []
@@ -1350,7 +1340,10 @@ def map_choice(obj):
 			syn.choices.append((dn, dn_list[0].split('=', 1)[1]))
 	elif issubclass(syn.__class__, udm_syntax.LDAP_Search):
 		options = options.get('options', {})
-		syntax = udm_syntax.LDAP_Search(options['syntax'], options['filter'], options['attributes'], options['base'], options['value'], options['viewonly'], options['empty'], options['empty_end'])
+		try:
+			syntax = udm_syntax.LDAP_Search(options['syntax'], options['filter'], options['attributes'], options['base'], options['value'], options['viewonly'], options['empty'], options['empty_end'])
+		except KeyError:
+			syntax = syn
 
 		if '$dn$' in options:
 			filter_mod = get_module(None, options['$dn$'])
@@ -1391,7 +1384,7 @@ def map_choice(obj):
 					id = obj.oldattr[store][0]
 				else:
 					# no valid store object, ignore
-					MODULE.warn('LDAP_Search syntax "%s": "%s" is no valid property for object "%s" - ignoring entry.' % (options['syntax'], store, dn))
+					MODULE.warn('LDAP_Search syntax %r: %r is no valid property for object %r - ignoring entry.' % (syntax.name, store, dn))
 					continue
 
 			# find the value to display