diff --git a/test/support/rdf_datatype_case.ex b/test/support/rdf_datatype_case.ex
index 25999cb..4861fe6 100644
--- a/test/support/rdf_datatype_case.ex
+++ b/test/support/rdf_datatype_case.ex
@@ -29,6 +29,8 @@ defmodule RDF.Datatype.Test.Case do
 
       import unquote(__MODULE__)
 
+      doctest unquote(datatype)
+
       @moduletag datatype: unquote(datatype)
 
       if unquote(valid) do