diff --git a/trealla/interop.go b/trealla/interop.go
index 6672d09..5347da0 100644
--- a/trealla/interop.go
+++ b/trealla/interop.go
@@ -90,14 +90,14 @@ func sys_coro_next_2(pl Prolog, subquery Subquery, goal Term) Term {
 	if !ok {
 		return throwTerm(domainError("integer", g.Args[0], g.pi()))
 	}
-	t, ok := plc.CoroNext(subquery, id)
-	if !ok || t == nil {
+	result, ok := plc.CoroNext(subquery, id)
+	if !ok || result == nil {
 		return Atom("fail")
 	}
-	// call(( Goal = Result ; '$coro_next'(ID, Goal) ))
+	// call(( wasm_generic:host_rpc_eval(Goal, Result, [], []) ; '$coro_next'(ID, Goal) ))
 	return Atom("call").Of(
 		Atom(";").Of(
-			Atom("=").Of(g.Args[1], t),
+			Atom(":").Of(Atom("wasm_generic"), Atom("host_rpc_eval").Of(result, g.Args[1], Atom("[]"), Atom("[]"))),
 			Atom("$coro_next").Of(id, g.Args[1]),
 		),
 	)
diff --git a/trealla/interop_test.go b/trealla/interop_test.go
index 40cc683..105e3be 100644
--- a/trealla/interop_test.go
+++ b/trealla/interop_test.go
@@ -207,7 +207,9 @@ func BenchmarkInteropNondet(b *testing.B) {
 			b.Fatal("query failed", query.Err())
 		}
 	}
-	query.Close()
+	if err := query.Close(); err != nil {
+		b.Error("close error:", err)
+	}
 	if leftovers := len(pl.(*prolog).coros); leftovers > 0 {
 		b.Error("coroutines weren't cleaned up:", leftovers)
 	}
diff --git a/trealla/terms/example_test.go b/trealla/terms/example_test.go
index d715379..03bf204 100644
--- a/trealla/terms/example_test.go
+++ b/trealla/terms/example_test.go
@@ -20,7 +20,7 @@ func Example_nondet_predicate() {
 	// betwixt(+Min, +Max, ?N).
 	pl.RegisterNondet(ctx, "betwixt", 3, func(_ trealla.Prolog, _ trealla.Subquery, goal0 trealla.Term) iter.Seq[trealla.Term] {
 		return func(yield func(trealla.Term) bool) {
-			// goal is the goal called by Prolog, such as: base32("hello", X).
+			// goal is the goal called by Prolog, such as: betwixt(1, 10, X).
 			// Guaranteed to match up with the registered arity and name.
 			goal := goal0.(trealla.Compound)