diff --git a/go/delivery/compose_candidate.go b/go/delivery/compose_candidate.go
index 26f051d..2420d61 100644
--- a/go/delivery/compose_candidate.go
+++ b/go/delivery/compose_candidate.go
@@ -148,6 +148,7 @@ func checkComposeAnswer(a ComposeCandidateAnswer) error {
 func strictDecode(data []byte, v any, what string) error {
 	d := json.NewDecoder(bytes.NewReader(data))
 	d.DisallowUnknownFields()
+	d.UseNumber() // a number in an object the contract leaves open (the composition input) keeps its digits as written
 	if err := d.Decode(v); err != nil {
 		return fmt.Errorf("delivery: %s does not fit its shape: %w", what, err)
 	}