diff --git a/cue/testdata/disjunctions/embed.txtar b/cue/testdata/disjunctions/embed.txtar
index 5d8e063..3a98652 100644
--- a/cue/testdata/disjunctions/embed.txtar
+++ b/cue/testdata/disjunctions/embed.txtar
@@ -159,10 +159,6 @@
           e: (string){ string }
         }, (#struct){
           d: (string){ string }
-        }, (#struct){
-          d: (string){ string }
-        }, (#struct){
-          d: (string){ string }
           e: (string){ string }
         }, (#struct){
           a: (string){ string }
@@ -186,12 +182,6 @@
         }, (#struct){
           a: (string){ string }
           d: (string){ string }
-        }, (#struct){
-          a: (string){ string }
-          d: (string){ string }
-        }, (#struct){
-          a: (string){ string }
-          d: (string){ string }
           e: (string){ string }
         }, (#struct){
           b: (string){ string }
@@ -215,12 +205,6 @@
         }, (#struct){
           b: (string){ string }
           d: (string){ string }
-        }, (#struct){
-          b: (string){ string }
-          d: (string){ string }
-        }, (#struct){
-          b: (string){ string }
-          d: (string){ string }
           e: (string){ string }
         }) }
       a: (struct){ |(*(#struct){
diff --git a/cue/types.go b/cue/types.go
index e78c41f..8e09deb 100644
--- a/cue/types.go
+++ b/cue/types.go
@@ -1831,7 +1831,7 @@
 	if v.v == nil || other.v == nil {
 		return false
 	}
-	return adt.Equal(v.ctx().opCtx, v.v, other.v, false)
+	return adt.Equal(v.ctx().opCtx, v.v, other.v, adt.CheckStructural)
 }
 
 // Format prints a debug version of a value.
diff --git a/internal/core/adt/disjunct.go b/internal/core/adt/disjunct.go
index 636f07d..f03a338 100644
--- a/internal/core/adt/disjunct.go
+++ b/internal/core/adt/disjunct.go
@@ -122,7 +122,7 @@
 	state VertexStatus,
 	parent *nodeContext,
 	parentMode defaultMode, // default mode of this disjunct
-	recursive bool) {
+	recursive, last bool) {
 
 	n.ctx.stats.DisjunctCount++
 
@@ -210,6 +210,7 @@
 			n.disjuncts = n.buffer[:0]
 			n.buffer = a[:0]
 
+			last := i+1 == len(n.disjunctions)
 			skipNonMonotonicChecks := i+1 < len(n.disjunctions)
 			if skipNonMonotonicChecks {
 				n.ctx.inDisjunct++
@@ -228,7 +229,7 @@
 
 						newMode := mode(d.hasDefaults, v.Default)
 
-						cn.expandDisjuncts(state, n, newMode, true)
+						cn.expandDisjuncts(state, n, newMode, true, last)
 					}
 
 				case d.value != nil:
@@ -241,7 +242,7 @@
 
 						newMode := mode(d.hasDefaults, i < d.value.NumDefaults)
 
-						cn.expandDisjuncts(state, n, newMode, true)
+						cn.expandDisjuncts(state, n, newMode, true, last)
 					}
 				}
 			}
@@ -365,7 +366,11 @@
 	outer:
 		for _, d := range n.disjuncts {
 			for k, v := range p.disjuncts {
-				if Equal(n.ctx, &v.result, &d.result, true) {
+				flags := CheckStructural
+				if last {
+					flags |= IgnoreOptional
+				}
+				if Equal(n.ctx, &v.result, &d.result, flags) {
 					m := maybeDefault
 					for _, u := range d.usedDefault {
 						m = combineDefault(m, u.nestedMode)
diff --git a/internal/core/adt/equality.go b/internal/core/adt/equality.go
index de57df9..d1b5a1d 100644
--- a/internal/core/adt/equality.go
+++ b/internal/core/adt/equality.go
@@ -14,17 +14,30 @@
 
 package adt
 
-func Equal(ctx *OpContext, v, w Value, optional bool) bool {
+type Flag uint16
+
+const (
+	// IgnoreOptional allows optional information to be ignored. This only
+	// applies when CheckStructural is given.
+	IgnoreOptional Flag = 1 << iota
+
+	// CheckStructural indicates that closedness information should be
+	// considered for equality. Equal may return false even when values are
+	// equal.
+	CheckStructural Flag = 1 << iota
+)
+
+func Equal(ctx *OpContext, v, w Value, flags Flag) bool {
 	if x, ok := v.(*Vertex); ok {
-		return equalVertex(ctx, x, w, optional)
+		return equalVertex(ctx, x, w, flags)
 	}
 	if y, ok := w.(*Vertex); ok {
-		return equalVertex(ctx, y, v, optional)
+		return equalVertex(ctx, y, v, flags)
 	}
-	return equalTerminal(ctx, v, w, optional)
+	return equalTerminal(ctx, v, w, flags)
 }
 
-func equalVertex(ctx *OpContext, x *Vertex, v Value, opt bool) bool {
+func equalVertex(ctx *OpContext, x *Vertex, v Value, flags Flag) bool {
 	y, ok := v.(*Vertex)
 	if !ok {
 		return false
@@ -47,7 +60,7 @@
 	if x.IsClosed(ctx) != y.IsClosed(ctx) {
 		return false
 	}
-	if opt && !equalClosed(ctx, x, y) {
+	if flags != 0 && !equalClosed(ctx, x, y, flags) {
 		return false
 	}
 
@@ -55,7 +68,7 @@
 	for _, a := range x.Arcs {
 		for _, b := range y.Arcs {
 			if a.Label == b.Label {
-				if !Equal(ctx, a, b, opt) {
+				if !Equal(ctx, a, b, flags) {
 					return false
 				}
 				continue loop1
@@ -81,7 +94,7 @@
 		return true // both are struct or list.
 	}
 
-	return equalTerminal(ctx, v, w, opt)
+	return equalTerminal(ctx, v, w, flags)
 }
 
 // equalClosed tests if x and y have the same set of close information.
@@ -93,16 +106,21 @@
 //
 // For all these refinements it would be necessary to have well-working
 // structure sharing so as to not repeatedly recompute optional arcs.
-func equalClosed(ctx *OpContext, x, y *Vertex) bool {
-	return verifyStructs(x, y) && verifyStructs(y, x)
+func equalClosed(ctx *OpContext, x, y *Vertex, flags Flag) bool {
+	return verifyStructs(x, y, flags) && verifyStructs(y, x, flags)
 }
 
-func verifyStructs(x, y *Vertex) bool {
+func verifyStructs(x, y *Vertex, flags Flag) bool {
 outer:
 	for _, s := range x.Structs {
-		if s.closeInfo == nil || s.closeInfo.span|DefinitionSpan == 0 {
+		if (flags&IgnoreOptional != 0) && !s.StructLit.HasOptional() {
 			continue
 		}
+		if s.closeInfo == nil || s.closeInfo.span&DefinitionSpan == 0 {
+			if !s.StructLit.HasOptional() {
+				continue
+			}
+		}
 		for _, t := range y.Structs {
 			if s.StructLit == t.StructLit {
 				continue outer
@@ -113,7 +131,7 @@
 	return true
 }
 
-func equalTerminal(ctx *OpContext, v, w Value, opt bool) bool {
+func equalTerminal(ctx *OpContext, v, w Value, flags Flag) bool {
 	if v == w {
 		return true
 	}
@@ -130,7 +148,7 @@
 
 	case *BoundValue:
 		if y, ok := w.(*BoundValue); ok {
-			return x.Op == y.Op && Equal(ctx, x.Value, y.Value, opt)
+			return x.Op == y.Op && Equal(ctx, x.Value, y.Value, flags)
 		}
 
 	case *BasicType:
@@ -145,7 +163,7 @@
 		}
 		// always ordered the same
 		for i, xe := range x.Values {
-			if !Equal(ctx, xe, y.Values[i], opt) {
+			if !Equal(ctx, xe, y.Values[i], flags) {
 				return false
 			}
 		}
@@ -159,7 +177,7 @@
 			return false
 		}
 		for i, xe := range x.Values {
-			if !Equal(ctx, xe, y.Values[i], opt) {
+			if !Equal(ctx, xe, y.Values[i], flags) {
 				return false
 			}
 		}
diff --git a/internal/core/adt/eval.go b/internal/core/adt/eval.go
index 7386e66..330c54b 100644
--- a/internal/core/adt/eval.go
+++ b/internal/core/adt/eval.go
@@ -306,7 +306,7 @@
 		if len(n.disjunctions) > 0 && disState != Finalized {
 			disState = Finalized
 		}
-		n.expandDisjuncts(disState, n, maybeDefault, false)
+		n.expandDisjuncts(disState, n, maybeDefault, false, true)
 
 		n.finalizeDisjuncts()
 
diff --git a/internal/core/adt/simplify.go b/internal/core/adt/simplify.go
index dea3066..4bf0876 100644
--- a/internal/core/adt/simplify.go
+++ b/internal/core/adt/simplify.go
@@ -214,7 +214,7 @@
 				return nil
 			}
 			for i, a := range x.Args {
-				if !Equal(ctx, a, y.Args[i], false) {
+				if !Equal(ctx, a, y.Args[i], CheckStructural) {
 					return nil
 				}
 			}