diff --git a/tests/70-xer-test-OK.asn1 b/tests/70-xer-test-OK.asn1
index c26b308..b26f105 100644
--- a/tests/70-xer-test-OK.asn1
+++ b/tests/70-xer-test-OK.asn1
@@ -19,7 +19,8 @@
 		sequence	Sequence,
 		set		Set,
 		setOf		SetOf,
-		seqOf		SeqOf
+		seqOf		SeqOf,
+		extensibleSet	ExtensibleSet
 	}
 
 	Sequence ::= SEQUENCE {
@@ -34,6 +35,11 @@
 		opaque		OCTET STRING	OPTIONAL
 	}
 
+	ExtensibleSet ::= SET {
+		string	UTF8String OPTIONAL,
+		...
+	}
+
 	SetOf ::= SET OF REAL
 	SeqOf ::= SEQUENCE OF id INTEGER