diff --git a/internal/core/adt/disjunct.go b/internal/core/adt/disjunct.go
index 7f3475f..e7db3cd 100644
--- a/internal/core/adt/disjunct.go
+++ b/internal/core/adt/disjunct.go
@@ -330,6 +330,7 @@
 // time that a clone is needed and must be nil. Conjuncts no longer needed and
 // can become nil. All other fields can be copied shallowly.
 func clone(v Vertex) Vertex {
+	v.state = nil
 	if a := v.Arcs; len(a) > 0 {
 		v.Arcs = make([]*Vertex, len(a))
 		for i, arc := range a {
diff --git a/internal/core/adt/eval.go b/internal/core/adt/eval.go
index b00b0b0..f873cf1 100644
--- a/internal/core/adt/eval.go
+++ b/internal/core/adt/eval.go
@@ -57,7 +57,18 @@
 	Allocs   int
 }
 
+// Leaks reports the number of nodeContext structs leaked. These are typically
+// benign, as they will just be garbage collected, as long as the pointer from
+// the original nodes has been eliminated or the original nodes are also not
+// referred to. But Leaks may have notable impact on performance, and thus
+// should be avoided.
+func (s *Stats) Leaks() int {
+	return s.Allocs + s.Reused - s.Freed
+}
+
 var stats = template.Must(template.New("stats").Parse(`{{"" -}}
+
+Leaks:  {{.Leaks}}
 Freed:  {{.Freed}}
 Reused: {{.Reused}}
 Allocs: {{.Allocs}}
@@ -330,10 +341,6 @@
 		}
 		n.expandDisjuncts(disState, n, maybeDefault, false)
 
-		// If the state has changed, it is because a disjunct has been run. In this case, our node will have completed, and it will
-		// set a value soon.
-		v.state = n // alternatively, set to nil
-
 		for _, d := range n.disjuncts {
 			d.free()
 		}
@@ -373,6 +380,11 @@
 			// TODO: how to represent closedness information? Do we need it?
 		}
 
+		// If the state has changed, it is because a disjunct has been run, or
+		// because a single disjunct has replaced it. Restore the old state as
+		// to not confuse memory management.
+		v.state = n
+
 		if state != Finalized {
 			return
 		}
diff --git a/internal/core/adt/eval_test.go b/internal/core/adt/eval_test.go
index 017a021..2f422be 100644
--- a/internal/core/adt/eval_test.go
+++ b/internal/core/adt/eval_test.go
@@ -64,7 +64,11 @@
 		ctx := e.NewContext(v)
 		v.Finalize(ctx)
 
-		t.Log(e.Stats())
+		stats := ctx.Stats()
+		t.Log(stats)
+		if n := stats.Leaks(); n > 0 {
+			t.Skipf("%d leaks reported", n)
+		}
 
 		if b := validate.Validate(ctx, v, &validate.Config{
 			AllErrors: true,