diff --git a/lib/asn1/canthandle.asn1 b/lib/asn1/canthandle.asn1
index b674476f1..7ec9077c0 100644
--- a/lib/asn1/canthandle.asn1
+++ b/lib/asn1/canthandle.asn1
@@ -31,4 +31,10 @@ Bar ::= SEQUENCE {
 
 Baz ::= SET OF INTEGER
 
+-- Allocation is done on CONTEXT tags.
+
+Alloc ::= SEQUENCE {
+	a heim_any OPTIONAL
+}
+
 END