diff --git a/crates/derive/keyfork-derive-openpgp/src/lib.rs b/crates/derive/keyfork-derive-openpgp/src/lib.rs
index 0fa727f..acfcee0 100644
--- a/crates/derive/keyfork-derive-openpgp/src/lib.rs
+++ b/crates/derive/keyfork-derive-openpgp/src/lib.rs
@@ -110,9 +110,16 @@ pub fn derive(data: DerivationResponse, keys: &[KeyFlags], userid: &UserID) -> R
         let subkey = if is_enc && is_non_enc {
             return Err(Error::InvalidKeyFlags(subkey_flags.clone()));
         } else if is_enc {
+            // Clamp key before exporting as OpenPGP. Reference:
+            // https://gitlab.com/sequoia-pgp/sequoia/-/blob/main/openpgp/src/crypto/backend/rust/asymmetric.rs (see: generate_ecc constructor)
+            // https://github.com/jedisct1/libsodium/blob/b4c5d37fb5ee2736caa4823433926b588911e893/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L91-L93
+            let mut bytes = PrivateKey::to_bytes(derived_key.private_key());
+            bytes[0] &= 0b1111_1000;
+            bytes[31] &= !0b1000_0000;
+            bytes[31] |= 0b0100_0000;
             Key::from(
                 Key4::<_, SubordinateRole>::import_secret_cv25519(
-                    &PrivateKey::to_bytes(derived_key.private_key()),
+                    &bytes,
                     None,
                     None,
                     epoch,