diff --git a/ucs-school-import/modules/ucsschool/importer/models/import_user.py b/ucs-school-import/modules/ucsschool/importer/models/import_user.py
index 392ce50..81e1d66 100644
--- a/ucs-school-import/modules/ucsschool/importer/models/import_user.py
+++ b/ucs-school-import/modules/ucsschool/importer/models/import_user.py
@@ -36,7 +36,7 @@ import datetime
 from collections import defaultdict
 from ldap.filter import filter_format
 
-from univention.admin.uexceptions import noObject
+from univention.admin.uexceptions import noObject, noProperty, valueError, valueInvalidSyntax
 from univention.admin import property as uadmin_property
 from ucsschool.lib.roles import role_pupil, role_teacher, role_staff
 from ucsschool.lib.models import Staff, Student, Teacher, TeachersAndStaff, User
@@ -147,13 +147,9 @@ class ImportUser(User):
 			self.logger.warn("Running create() from within a hook.")
 			return self.create_without_hooks(lo, validate)
 		else:
+			self._check_consistency()
 			return super(ImportUser, self).create(lo, validate)
 
-	def create_without_hooks(self, lo, validate):
-		success = super(ImportUser, self).create_without_hooks(lo, validate)
-		self.store_udm_properties(lo)
-		return success
-
 	@classmethod
 	def get_by_import_id(cls, connection, source_uid, record_uid, superordinate=None):
 		"""
@@ -191,6 +187,15 @@ class ImportUser(User):
 		if self._userexpiry is not None:
 			udm_obj["userexpiry"] = self._userexpiry
 
+		for property_, value in (self.udm_properties or {}).items():
+			try:
+				udm_obj[property_] = value
+			except (KeyError, noProperty) as exc:
+				raise UnknownProperty("UDM properties could not be set. Unknown property: '{}'".format(exc),
+					entry=self.entry_count, import_user=self)
+			except (valueError, valueInvalidSyntax) as exc:
+				raise  # TODO: maybe another importer subclass?
+
 	def has_expired(self, connection):
 		"""
 		Check if the user account has expired.
@@ -492,16 +497,13 @@ class ImportUser(User):
 			return super(ImportUser, self).modify(lo, validate, move_if_necessary)
 
 	def modify_without_hooks(self, lo, validate=True, move_if_necessary=None):
-		# must set udm_properties first, as they contain overridePWHistory and
-		# overridePWLength
-		self.store_udm_properties(lo)
+		self._check_consistency()
 		if not self.school_classes:
 			# empty classes input means: don't change existing classes (Bug #42288)
 			self.logger.debug("No school_classes are set, not modifying existing ones.")
 			udm_obj = self.get_udm_object(lo)
 			self.school_classes = self.get_school_classes(udm_obj, self)
-		success = super(ImportUser, self).modify_without_hooks(lo, validate, move_if_necessary)
-		return success
+		return super(ImportUser, self).modify_without_hooks(lo, validate, move_if_necessary)
 
 	def move(self, lo, udm_obj=None, force=False):
 		self._lo = lo
@@ -728,14 +730,10 @@ class ImportUser(User):
 				for meth_name, meths in self._pyhook_cache.items()]))
 		return pyhooks
 
-	def store_udm_properties(self, connection):
-		"""
-		Copy data from self.udm_properties into UDM object of this user.
-
-		:param connection: LDAP connection
-		"""
+	def _check_consistency(self):
 		if not self.udm_properties:
 			return
+
 		forbidden_attributes = {"birthday", "disabled", "firstname", "lastname",
 			"mailPrimaryAddress", "name", "password", "school", "schools", "school_classes", "sn", "uid", "username"}
 		bad_props = set(self.udm_properties.keys()).intersection(forbidden_attributes)
@@ -747,14 +745,6 @@ class ImportUser(User):
 			"address is strored in the 'email' attribute of the {} object (not in udm_properties).".format(
 				self.__class__.__name__))
 
-		udm_obj = self.get_udm_object(connection)
-		udm_obj.info.update(self.udm_properties)
-		try:
-			udm_obj.modify()
-		except KeyError as exc:
-			raise UnknownProperty("UDM properties could not be set. Unknown property: '{}'".format(exc),
-				entry=self.entry_count, import_user=self)
-
 	def update(self, other):
 		"""
 		Copy attributes of other ImportUser into this one.