Fix typo that made limit required on symbol

diff --git a/docbook/relaxng/docbook/src/pool.rnc b/docbook/relaxng/docbook/src/pool.rnc
index facc47d83e9cfc8aa98382ab681d016c8508f565..868a71b443c290741265a51342630ce363c0b7a2 100644 (file)
--- a/docbook/relaxng/docbook/src/pool.rnc
+++ b/docbook/relaxng/docbook/src/pool.rnc
@@ -6567,7 +6567,7 @@ div {
       db.symbol.role.attribute?
     & db.common.attributes
     & db.common.linking.attributes
-    & db.symbol.class.attribute
+    & db.symbol.class.attribute?
 
    db.symbol =
       element symbol {