diff --git a/src/pkcs1v15.rs b/src/pkcs1v15.rs
index dc9a94d3..5fb377e8 100644
--- a/src/pkcs1v15.rs
+++ b/src/pkcs1v15.rs
@@ -4,7 +4,7 @@ use core::fmt::{Debug, Display, Formatter, LowerHex, UpperHex};
 use core::marker::PhantomData;
 use core::ops::Deref;
 use digest::Digest;
-use pkcs8::{AssociatedOid, Document, EncodePublicKey};
+use pkcs8::{AssociatedOid, Document, EncodePrivateKey, EncodePublicKey, SecretDocument};
 use rand_core::{CryptoRng, RngCore};
 #[cfg(feature = "hazmat")]
 use signature::hazmat::{PrehashSigner, PrehashVerifier};
@@ -376,6 +376,15 @@ where
     }
 }
 
+impl<D> EncodePrivateKey for SigningKey<D>
+where
+    D: Digest,
+{
+    fn to_pkcs8_der(&self) -> pkcs8::Result<SecretDocument> {
+        self.inner.to_pkcs8_der()
+    }
+}
+
 impl<D> Signer<Signature> for SigningKey<D>
 where
     D: Digest,
diff --git a/src/pss.rs b/src/pss.rs
index 69704416..e9a8953e 100644
--- a/src/pss.rs
+++ b/src/pss.rs
@@ -5,7 +5,7 @@ use core::fmt::{Debug, Display, Formatter, LowerHex, UpperHex};
 use core::marker::PhantomData;
 use core::ops::Deref;
 use digest::{Digest, DynDigest, FixedOutputReset};
-use pkcs8::{Document, EncodePublicKey};
+use pkcs8::{Document, EncodePrivateKey, EncodePublicKey, SecretDocument};
 use rand_core::{CryptoRng, RngCore};
 #[cfg(feature = "hazmat")]
 use signature::hazmat::{PrehashVerifier, RandomizedPrehashSigner};
@@ -574,6 +574,15 @@ where
     }
 }
 
+impl<D> EncodePrivateKey for SigningKey<D>
+where
+    D: Digest,
+{
+    fn to_pkcs8_der(&self) -> pkcs8::Result<SecretDocument> {
+        self.inner.to_pkcs8_der()
+    }
+}
+
 impl<D> RandomizedSigner<Signature> for SigningKey<D>
 where
     D: Digest + FixedOutputReset,
@@ -688,6 +697,15 @@ where
     }
 }
 
+impl<D> EncodePrivateKey for BlindedSigningKey<D>
+where
+    D: Digest,
+{
+    fn to_pkcs8_der(&self) -> pkcs8::Result<SecretDocument> {
+        self.inner.to_pkcs8_der()
+    }
+}
+
 impl<D> RandomizedSigner<Signature> for BlindedSigningKey<D>
 where
     D: Digest + FixedOutputReset,