diff --git a/lib/iev/termbase/term_builder.rb b/lib/iev/termbase/term_builder.rb
index cb5df23..5ffc676 100644
--- a/lib/iev/termbase/term_builder.rb
+++ b/lib/iev/termbase/term_builder.rb
@@ -327,7 +327,7 @@ def html_entities_to_stem(x)
       end
 
       def mathml_to_asciimath(input)
-        return input if input.nil? || input.empty?
+        return input if input.nil? || input.empty? || !input.include?("<")
 
         unless input.match?(/<math>/)
           return html_to_asciimath(input)