diff --git a/lib/rdf/literal/datatypes/lang_string.ex b/lib/rdf/literal/datatypes/lang_string.ex
index 88c0584..063b48b 100644
--- a/lib/rdf/literal/datatypes/lang_string.ex
+++ b/lib/rdf/literal/datatypes/lang_string.ex
@@ -126,7 +126,7 @@ defmodule RDF.LangString do
     do: match_language?(language_tag, language_range)
 
   def match_language?("", "*"), do: false
-  def match_language?(_, "*"),  do: true
+  def match_language?(str, "*") when is_binary(str), do: true
 
   def match_language?(language_tag, language_range)
       when is_binary(language_tag) and is_binary(language_range) do
diff --git a/test/unit/datatypes/lang_string_test.exs b/test/unit/datatypes/lang_string_test.exs
index c3a6b49..ae142b3 100644
--- a/test/unit/datatypes/lang_string_test.exs
+++ b/test/unit/datatypes/lang_string_test.exs
@@ -291,6 +291,7 @@ defmodule RDF.LangStringTest do
     test "with a non-language-tagged literal" do
       refute XSD.String.new("42") |> LangString.match_language?("de")
       refute XSD.String.new("42") |> LangString.match_language?("")
+      refute XSD.String.new("42") |> LangString.match_language?("*")
       refute XSD.Integer.new("42") |> LangString.match_language?("de")
     end
   end