diff --git a/ada/nodes.lkt b/ada/nodes.lkt
index d53107010..c4e4ba896 100644
--- a/ada/nodes.lkt
+++ b/ada/nodes.lkt
@@ -6621,6 +6621,7 @@ class SubtypeDecl: BaseSubtypeDecl {
         case t => t
     }
 
+    @memoized
     fun get_imp_deref(): Entity[Expr] =
        self.get_type().get_imp_deref()