diff --git a/lib/json/ld/context/term_definition.ex b/lib/json/ld/context/term_definition.ex
index fb1716c..4bc3c29 100644
--- a/lib/json/ld/context/term_definition.ex
+++ b/lib/json/ld/context/term_definition.ex
@@ -1,7 +1,7 @@
 defmodule JSON.LD.Context.TermDefinition do
   defstruct iri_mapping: nil,
             reverse_property: false,
-            type_mapping: nil, language_mapping: :undefined,
+            type_mapping: nil, language_mapping: false,
             container_mapping: nil
 
 end