diff --git a/schema/legacy/eoa-tei-strict.rnc b/schema/legacy/eoa-tei-strict.rnc
index 9ffe364..9dcf597 100644
--- a/schema/legacy/eoa-tei-strict.rnc
+++ b/schema/legacy/eoa-tei-strict.rnc
@@ -579,7 +579,7 @@ markup =
 hi =
    element hi {
       attribute  rend { "italic" | "superscript" | "subscript" | "math" | "bold" | "struck" | "spaced" | "smallcaps" },
-      ( text | index | indexanchor )+
+      ( text | index | indexanchor | ref )+
    }
 
 theorem =