diff --git a/spec/index.html b/spec/index.html
index beb5ea5..8c5517a 100644
--- a/spec/index.html
+++ b/spec/index.html
@@ -435,7 +435,7 @@ <h2>Simple Interpretations</h2>
     is a set of pairs which identify the arguments for which the property is true,
     that is, a binary relational extension.</p>
 
-  <p>The distinction between IR and IL will become significant below when the semantics of datatypes are defined.
+  <p>The distinction between IS and IL will become significant below when the semantics of datatypes are defined.
     IL is allowed to be partial because some literals may fail to have a referent. </p>
 
   <p class="technote">It is conventional to map a relation name to a relational extension directly.