diff --git a/conversion_utils/jos_msds_and_properties.py b/conversion_utils/jos_msds_and_properties.py
index 0bddd2b..2751ec1 100644
--- a/conversion_utils/jos_msds_and_properties.py
+++ b/conversion_utils/jos_msds_and_properties.py
@@ -4,7 +4,7 @@ import sys
 
 from conversion_utils.utils import xpath_find, get_xml_id
 
-LANGUAGE_INDEX_MAP = {'en':0, 'sl':1}
+LANGUAGES = ['en', 'sl']
 
 LEXEME_FEATURE_MAP = {'noun':{1,2},
                       'verb':{1,2},
@@ -156,7 +156,7 @@ class SpecificationsBuilder:
 class Properties:
 
     def __init__(self, lemma, category, feature_value_list, language_index):
-        self.language = next(l for (l, i) in LANGUAGE_INDEX_MAP.items() if i == language_index)
+        self.language = LANGUAGES[language_index]
         self.category = category.string_pair[language_index]
         self.lexeme_feature_map = {}
         self.form_feature_map = {}
@@ -175,13 +175,23 @@ class Properties:
             format(language=self.language, category=self.category, lexeme_features=str(self.lexeme_feature_map), form_features=str(self.form_feature_map))
 
 
+class Msd:
+
+    def __init__(self, code, language):
+        self.code = code
+        self.language = language
+
+    def __str__(self):
+        return 'code={code}, language={language}'.format(code=self.code, language=self.language)
+
+
 class MsdToProperties:
 
-    def convert(self, specifications, lemma, msd, msd_language, properties_language):
-        msd_language_index = LANGUAGE_INDEX_MAP[msd_language]
-        properties_language_index = LANGUAGE_INDEX_MAP[properties_language]
-        category_char = msd[0].lower()
-        value_chars = msd[1:]
+    def convert(self, specifications, msd, lemma, properties_language):
+        msd_language_index = LANGUAGES.index(msd.language)
+        properties_language_index = LANGUAGES.index(properties_language)
+        category_char = msd.code[0].lower()
+        value_chars = msd.code[1:]
         category = specifications.find_category(category_char, msd_language_index)
         feature_value_list = []
         for (index, value_char) in enumerate(value_chars, start=1):
diff --git a/tests/test_jos_msd_to_properties.py b/tests/test_jos_msd_to_properties.py
index 7307e0f..4b33e4d 100644
--- a/tests/test_jos_msd_to_properties.py
+++ b/tests/test_jos_msd_to_properties.py
@@ -2,7 +2,7 @@ import os.path
 import lxml.etree as lxml
 import unittest
 
-from conversion_utils.jos_msds_and_properties import SpecificationsBuilder, MsdToProperties
+from conversion_utils.jos_msds_and_properties import SpecificationsBuilder, MsdToProperties, Msd
 
 class JosMsdToPropertiesTestCase(unittest.TestCase):
 
@@ -13,49 +13,49 @@ class JosMsdToPropertiesTestCase(unittest.TestCase):
         self.converter = MsdToProperties()
 
     def test_en_en(self):
-        properties = self.converter.convert(self.specifications, 'miza', 'Ncfpd', 'en', 'en')
+        properties = self.converter.convert(self.specifications, Msd('Ncfpd', 'en'), 'miza', 'en')
         self.assertEqual(properties.language, 'en')
         self.assertEqual(properties.category, 'noun')
         self.assertEqual(properties.lexeme_feature_map, {'type':'common', 'gender':'feminine'})
         self.assertEqual(properties.form_feature_map, {'number':'plural', 'case':'dative'})
 
     def test_en_sl(self):
-        properties = self.converter.convert(self.specifications, 'miza', 'Ncfpd', 'en', 'sl')
+        properties = self.converter.convert(self.specifications, Msd('Ncfpd', 'en'), 'miza', 'sl')
         self.assertEqual(properties.language, 'sl')
         self.assertEqual(properties.category, 'samostalnik')
         self.assertEqual(properties.lexeme_feature_map, {'vrsta':'občno_ime', 'spol':'ženski'})
         self.assertEqual(properties.form_feature_map, {'število':'množina', 'sklon':'dajalnik'})
 
     def test_sl_en(self):
-        properties = self.converter.convert(self.specifications, 'miza', 'Sozmd', 'sl', 'en')
+        properties = self.converter.convert(self.specifications, Msd('Sozmd', 'sl'), 'miza', 'en')
         self.assertEqual(properties.language, 'en')
         self.assertEqual(properties.category, 'noun')
         self.assertEqual(properties.lexeme_feature_map, {'type':'common', 'gender':'feminine'})
         self.assertEqual(properties.form_feature_map, {'number':'plural', 'case':'dative'})
 
     def test_sl_sl(self):
-        properties = self.converter.convert(self.specifications, 'miza', 'Sozmd', 'sl', 'sl')
+        properties = self.converter.convert(self.specifications, Msd('Sozmd', 'sl'), 'miza', 'sl')
         self.assertEqual(properties.language, 'sl')
         self.assertEqual(properties.category, 'samostalnik')
         self.assertEqual(properties.lexeme_feature_map, {'vrsta':'občno_ime', 'spol':'ženski'})
         self.assertEqual(properties.form_feature_map, {'število':'množina', 'sklon':'dajalnik'})
 
     def test_exception_feature_level(self): # testing level exception: ('pronoun', 8, 'ti')
-        properties = self.converter.convert(self.specifications, 'ti', 'Pp2-sd--y', 'en', 'sl')
+        properties = self.converter.convert(self.specifications, Msd('Pp2-sd--y', 'en'), 'ti', 'sl')
         self.assertEqual(properties.language, 'sl')
         self.assertEqual(properties.category, 'zaimek')
         self.assertEqual(properties.lexeme_feature_map, {'vrsta':'osebni', 'oseba':'druga'})
         self.assertEqual(properties.form_feature_map, {'število':'ednina', 'sklon':'dajalnik', 'naslonskost':'klitična'})
 
     def test_normal_feature_level(self): # invalid msd, but useful for testing contrast with previous test
-        properties = self.converter.convert(self.specifications, 'vi', 'Pp2-pd--y', 'en', 'sl')
+        properties = self.converter.convert(self.specifications, Msd('Pp2-pd--y', 'en'), 'vi', 'sl')
         self.assertEqual(properties.language, 'sl')
         self.assertEqual(properties.category, 'zaimek')
         self.assertEqual(properties.lexeme_feature_map, {'vrsta':'osebni', 'oseba':'druga', 'naslonskost':'klitična'})
         self.assertEqual(properties.form_feature_map, {'število':'množina', 'sklon':'dajalnik'})
 
     def test_featureless(self):
-        properties = self.converter.convert(self.specifications, 'in', 'V', 'sl', 'en')
+        properties = self.converter.convert(self.specifications, Msd('V', 'sl'), 'in', 'en')
         self.assertEqual(properties.language, 'en')
         self.assertEqual(properties.category, 'conjunction')
         self.assertEqual(properties.lexeme_feature_map, {})