diff --git a/cue/testdata/eval/closed_disjunction.txtar b/cue/testdata/eval/closed_disjunction.txtar
index 3bab475..b0c2132 100644
--- a/cue/testdata/eval/closed_disjunction.txtar
+++ b/cue/testdata/eval/closed_disjunction.txtar
@@ -32,8 +32,11 @@
 Result:
 (_|_){
   // [eval]
-  #A: (#struct){
-  }
+  #A: (struct){ |(*(#struct){
+    }, (#struct){
+    }, (#struct){
+    }, (#struct){
+    }) }
   a: (#struct){
     b: (int){ 3 }
     c: (int){ 3 }
diff --git a/cue/testdata/eval/issue353.txtar b/cue/testdata/eval/issue353.txtar
index 10216af..9b26d24 100644
--- a/cue/testdata/eval/issue353.txtar
+++ b/cue/testdata/eval/issue353.txtar
@@ -13,12 +13,16 @@
 }
 -- out/eval --
 (struct){
-  e: (#struct){
-    a: (string){ "hello" }
-  }
-  #Example: (#struct){
-    a: (string){ string }
-  }
+  e: (struct){ |((#struct){
+      a: (string){ "hello" }
+    }, (#struct){
+      a: (string){ "hello" }
+    }) }
+  #Example: (struct){ |((#struct){
+      a: (string){ string }
+    }, (#struct){
+      a: (string){ string }
+    }) }
 }
 -- out/compile --
 --- in.cue
diff --git a/internal/core/adt/equality.go b/internal/core/adt/equality.go
index c8a7d9c..ca7b41f 100644
--- a/internal/core/adt/equality.go
+++ b/internal/core/adt/equality.go
@@ -47,6 +47,9 @@
 	if x.IsClosed(ctx) != y.IsClosed(ctx) {
 		return false
 	}
+	if !equalOptional(ctx, x, y) {
+		return false
+	}
 
 loop1:
 	for _, a := range x.Arcs {
@@ -81,6 +84,37 @@
 	return equalTerminal(ctx, v, w)
 }
 
+// equalOptional tests if x and y have the same set of close information.
+// Right now this just checks if it has the same source structs that
+// define optional fields.
+// TODO: the following refinements are possible:
+// - unify optional fields and equate the optional fields
+// - do the same for pattern constraints, where the pattern constraints
+//   are collated by pattern equality.
+// - a further refinement would collate patterns by ranges.
+//
+// For all these refinements it would be necessary to have well-working
+// structure sharing so as to not repeatedly recompute optional arcs.
+func equalOptional(ctx *OpContext, x, y *Vertex) bool {
+	return verifyStructs(x, y) && verifyStructs(y, x)
+}
+
+func verifyStructs(x, y *Vertex) bool {
+outer:
+	for _, s := range x.Structs {
+		if !s.StructLit.HasOptional() {
+			continue
+		}
+		for _, t := range y.Structs {
+			if s.StructLit == t.StructLit {
+				continue outer
+			}
+		}
+		return false
+	}
+	return true
+}
+
 func equalTerminal(ctx *OpContext, v, w Value) bool {
 	if v == w {
 		return true