diff --git a/internal/link/enrol_proof_test.go b/internal/link/enrol_proof_test.go
new file mode 100644
index 0000000..727197f
--- /dev/null
+++ b/internal/link/enrol_proof_test.go
@@ -0,0 +1,13 @@
+package link
+
+import "testing"
+
+// The bytes a node signs when it enrols, built here to check its signature. The host builds the
+// same bytes in another repository; this known answer is repeated in its test, so the two cannot
+// drift apart without one of them failing (novox/hq issue 083).
+func TestWhatAnEnrollingNodeSignsIsFixed(t *testing.T) {
+	got := string(EnrolProof("s", []byte{1, 2, 3}, "o", "e", "v"))
+	if want := "novox-mesh-enrol\x00s\x00AQID\x00o\x00e\x00v"; got != want {
+		t.Fatalf("the enrolment proof's message changed: %q, want %q", got, want)
+	}
+}