diff --git a/mopidy/compat.py b/mopidy/compat.py
index 5df43e74..97531df7 100644
--- a/mopidy/compat.py
+++ b/mopidy/compat.py
@@ -34,6 +34,7 @@ if PY2:
     text_type = unicode
 
     input = raw_input
+    intern = intern
 
     def itervalues(dct, **kwargs):
         return iter(dct.itervalues(**kwargs))
@@ -49,6 +50,7 @@ else:
     text_type = str
 
     input = input
+    intern = sys.intern
 
     def itervalues(dct, **kwargs):
         return iter(dct.values(**kwargs))
diff --git a/mopidy/models/fields.py b/mopidy/models/fields.py
index 91cd2cad..c686b447 100644
--- a/mopidy/models/fields.py
+++ b/mopidy/models/fields.py
@@ -95,7 +95,7 @@ class Identifier(String):
     :param default: default value for field
     """
     def validate(self, value):
-        return intern(str(super(Identifier, self).validate(value)))
+        return compat.intern(str(super(Identifier, self).validate(value)))
 
 
 class URI(Identifier):