diff --git a/src/caosdb/apiutils.py b/src/caosdb/apiutils.py
index 37599d57c61be6d6209b410dcf238c5807a2995e..3af9345e48941d5f61766cc1c9d49a4a7b9c4fcb 100644
--- a/src/caosdb/apiutils.py
+++ b/src/caosdb/apiutils.py
@@ -86,11 +86,11 @@ def new_record(record_type, name=None, description=None,
 def id_query(ids):
     q = "FIND Entity with " + " OR ".join(["id={}".format(id) for id in ids])
 
-    return db.execute_query(q)
+    return execute_query(q)
 
 
 def retrieve_entities_with_ids(entities):
-    collection = db.Container()
+    collection = Container()
     step = 20
 
     for i in range(len(entities)//step+1):
diff --git a/src/caosdb/common/datatype.py b/src/caosdb/common/datatype.py
index f40b79f9819ea74461f8fcf7135f9baff69ac526..23b01a8a5db36e39d00e78f26c7de08a8bfb5f42 100644
--- a/src/caosdb/common/datatype.py
+++ b/src/caosdb/common/datatype.py
@@ -43,7 +43,7 @@ def LIST(datatype):
 
 def get_list_datatype(datatype):
     """ returns the datatype of the elements in the list """
-    match = re.match("LIST(<|&lt;)(?P<datatype>.*)(>|&gt;)", "LISTING")
+    match = re.match("LIST(<|&lt;)(?P<datatype>.*)(>|&gt;)", datatype)
 
     if match is not None:
         return match.group("datatype")
@@ -109,7 +109,7 @@ def get_id_of_datatype(datatype):
         raise AmbiguityException(
             "Name {} did not lead to unique result; Missing "
             "implementation".format(datatype))
-    elif len(res) == 1:
+    elif len(res) != 1:
         raise EntityDoesNotExistError(
             "No RecordType named {}".format(datatype))
 
diff --git a/src/caosdb/common/models.py b/src/caosdb/common/models.py
index f9d4f2b07b075eda7d50394c4f95a113f815a5bf..32343680f1ffc8a3b2eb53302c10e67101cc93f6 100644
--- a/src/caosdb/common/models.py
+++ b/src/caosdb/common/models.py
@@ -38,8 +38,8 @@ from sys import hexversion
 from tempfile import NamedTemporaryFile
 from warnings import warn
 
-from lxml import etree
-from .datatype import is_reference
+from caosdb.common.datatype import (BOOLEAN, DATETIME, DOUBLE, FILE, INTEGER,
+                                    LIST, REFERENCE, TEXT, is_reference)
 from caosdb.common.utils import uuid, xml2str
 from caosdb.configuration import get_config
 from caosdb.connection.connection import get_connection
@@ -50,8 +50,9 @@ from caosdb.exceptions import (AmbiguityException, AuthorizationException,
                                EntityHasNoDatatypeError, TransactionError,
                                UniqueNamesError, UnqualifiedParentsError,
                                UnqualifiedPropertiesError, URITooLongException)
-from caosdb.common.datatype import (BOOLEAN, DATETIME, DOUBLE, FILE, INTEGER,
-                                    LIST, REFERENCE, TEXT, is_reference)
+from lxml import etree
+
+from .datatype import is_reference
 
 _ENTITY_URI_SEGMENT = "Entity"
 
@@ -953,7 +954,8 @@ class Entity(object):
                 if isinstance(prop.value, list):
                     prop.value = [func(el) for el in prop.value]
                 else:
-                    prop.value = func(prop.value)
+                    if prop.value is not None:
+                        prop.value = func(prop.value)
 
 
 def _parse_col_values(cdt, vals):