diff --git a/client/internal/pqkem/message.go b/client/internal/pqkem/message.go
index 341f6b5f8..fe4381636 100644
--- a/client/internal/pqkem/message.go
+++ b/client/internal/pqkem/message.go
@@ -82,9 +82,10 @@ func (m *AnswerMsg) Encode() ([]byte, error) {
 	return frame(MsgAnswer, m.ExchangeID, m.KEMAnswer), nil
 }
 
-// Encode serialises the confirm with its framed header.
-func (m *ConfirmMsg) Encode() []byte {
-	return frame(MsgConfirm, m.ExchangeID, nil)
+// Encode serialises the confirm with its framed header. It returns an error only
+// for signature uniformity with the other messages; it never actually fails.
+func (m *ConfirmMsg) Encode() ([]byte, error) {
+	return frame(MsgConfirm, m.ExchangeID, nil), nil
 }
 
 // Decode parses a framed message into one of *OfferMsg / *AnswerMsg / *ConfirmMsg.
diff --git a/client/internal/pqkem/message_test.go b/client/internal/pqkem/message_test.go
index a51135ea0..1845bc4d9 100644
--- a/client/internal/pqkem/message_test.go
+++ b/client/internal/pqkem/message_test.go
@@ -29,7 +29,8 @@ func TestMessageRoundTrip(t *testing.T) {
 	require.Equal(t, MsgAnswer, typ)
 	require.Equal(t, answer, decoded.(*AnswerMsg).KEMAnswer)
 
-	confBytes := (&ConfirmMsg{ExchangeID: id}).Encode()
+	confBytes, err := (&ConfirmMsg{ExchangeID: id}).Encode()
+	require.NoError(t, err)
 	typ, decoded, err = Decode(confBytes)
 	require.NoError(t, err)
 	require.Equal(t, MsgConfirm, typ)