diff --git a/hpke/kem_test.go b/hpke/kem_test.go
new file mode 100644
index 000000000..c536133ac
--- /dev/null
+++ b/hpke/kem_test.go
@@ -0,0 +1,63 @@
+package hpke_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/cloudflare/circl/hpke"
+	"github.com/cloudflare/circl/internal/test"
+)
+
+func TestKemKeysMarshal(t *testing.T) {
+	for _, kem := range []hpke.KEM{
+		hpke.KEM_P256_HKDF_SHA256,
+		hpke.KEM_P384_HKDF_SHA384,
+		hpke.KEM_P521_HKDF_SHA512,
+		hpke.KEM_X25519_HKDF_SHA256,
+		hpke.KEM_X448_HKDF_SHA512,
+		hpke.KEM_X25519_KYBER768_DRAFT00,
+	} {
+		checkIssue488(t, kem)
+	}
+}
+
+func checkIssue488(t *testing.T, kem hpke.KEM) {
+	scheme := kem.Scheme()
+	pk, sk, err := scheme.GenerateKeyPair()
+	if err != nil {
+		t.Fatal(err)
+	}
+	skBytes, err := sk.MarshalBinary()
+	test.CheckNoErr(t, err, "marshal private key")
+	pkBytes, err := pk.MarshalBinary()
+	test.CheckNoErr(t, err, "marshal public key")
+
+	t.Run(fmt.Sprintf("%v/PrivateKey", scheme.Name()), func(t *testing.T) {
+		N := scheme.PrivateKeySize()
+		buffer := make([]byte, N+1)
+		copy(buffer, skBytes)
+
+		// passing a buffer larger than the private key size should error (but no panic).
+		_, err := scheme.UnmarshalBinaryPrivateKey(buffer[:N+1])
+		test.CheckIsErr(t, err, "unmarshal private key should failed")
+
+		// passing a buffer of the exact size must be correct.
+		gotSk, err := scheme.UnmarshalBinaryPrivateKey(buffer[:N])
+		test.CheckNoErr(t, err, "unmarshal private key shouldn't fail")
+		test.CheckOk(sk.Equal(gotSk), "private keys are not equal", t)
+	})
+
+	t.Run(fmt.Sprintf("%v/PublicKey", scheme.Name()), func(t *testing.T) {
+		N := scheme.PublicKeySize()
+		buffer := make([]byte, N+1)
+		copy(buffer, pkBytes)
+
+		// passing a buffer larger than the public key size should error (but no panic).
+		_, err := scheme.UnmarshalBinaryPublicKey(buffer[:N+1])
+		test.CheckIsErr(t, err, "unmarshal public key should failed")
+
+		gotPk, err := scheme.UnmarshalBinaryPublicKey(buffer[:N])
+		test.CheckNoErr(t, err, "unmarshal public key shouldn't fail")
+		test.CheckOk(pk.Equal(gotPk), "public keys are not equal", t)
+	})
+}