diff --git a/transition_machine/src/Oracle.cpp b/transition_machine/src/Oracle.cpp
index 81c3ca1f791c3a567b6e3b1d241ea3a94ff4616d..805b62c455cdeeb99fada7d4bff0e5fce9354ebe 100644
--- a/transition_machine/src/Oracle.cpp
+++ b/transition_machine/src/Oracle.cpp
@@ -419,7 +419,7 @@ void Oracle::createDatabase()
   {
     const std::string & form = c.getTape("FORM").getRef(0);
     const std::string & lemma = c.getTape("LEMMA").getRef(0);
-    std::string rule = getRule(form, lemma);
+    std::string rule = getRule(toLowerCase(form), toLowerCase(lemma));
 
     return (action == std::string("RULE LEMMA ON FORM ") + rule || c.endOfTapes()) ? 0 : 1;
   })));