diff --git a/openssl-sys/src/lib.rs b/openssl-sys/src/lib.rs
index 63714b7e..517707c3 100644
--- a/openssl-sys/src/lib.rs
+++ b/openssl-sys/src/lib.rs
@@ -1761,10 +1761,14 @@ extern {
 
     pub fn d2i_X509(a: *mut *mut X509, pp: *mut *const c_uchar, length: c_long) -> *mut X509;
     pub fn i2d_X509_bio(b: *mut BIO, x: *mut X509) -> c_int;
+    pub fn i2d_X509(x: *mut X509, buf: *mut *mut u8) -> c_int;
     pub fn i2d_X509_REQ_bio(b: *mut BIO, x: *mut X509_REQ) -> c_int;
+    pub fn i2d_X509_REQ(x: *mut X509_REQ, buf: *mut *mut u8) -> c_int;
 
     pub fn i2d_PUBKEY_bio(b: *mut BIO, x: *mut EVP_PKEY) -> c_int;
     pub fn i2d_PrivateKey_bio(b: *mut BIO, x: *mut EVP_PKEY) -> c_int;
+    pub fn i2d_PUBKEY(k: *mut EVP_PKEY, buf: *mut *mut u8) -> c_int;
+    pub fn i2d_PrivateKey(k: *mut EVP_PKEY, buf: *mut *mut u8) -> c_int;
 
     pub fn i2d_RSA_PUBKEY(k: *mut RSA, buf: *mut *mut u8) -> c_int;
     pub fn d2i_RSA_PUBKEY(k: *mut *mut RSA, buf: *mut *const u8, len: c_long) -> *mut RSA;
diff --git a/openssl/src/dh.rs b/openssl/src/dh.rs
index ad1ebf9f..2b0a1508 100644
--- a/openssl/src/dh.rs
+++ b/openssl/src/dh.rs
@@ -22,15 +22,7 @@ impl DhRef {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Encodes the parameters to DER.
-    pub fn to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_DHparams(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_DHparams(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
+    to_der!(ffi::i2d_DHparams);
 }
 
 impl Dh {
diff --git a/openssl/src/dsa.rs b/openssl/src/dsa.rs
index 9afb952e..0444ed9f 100644
--- a/openssl/src/dsa.rs
+++ b/openssl/src/dsa.rs
@@ -25,25 +25,8 @@ impl DsaRef {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Encodes a DSA private key as unencrypted DER formatted data.
-    pub fn private_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_DSAPrivateKey(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_DSAPrivateKey(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
-
-    /// Encodes a DSA public key as DER formatted data.
-    pub fn public_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_DSAPublicKey(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_DSAPublicKey(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
+    private_key_to_der!(ffi::i2d_DSAPrivateKey);
+    public_key_to_der!(ffi::i2d_DSAPublicKey);
 
     // FIXME should return u32
     pub fn size(&self) -> Option<u32> {
diff --git a/openssl/src/ec_key.rs b/openssl/src/ec_key.rs
index 7406572a..706265ef 100644
--- a/openssl/src/ec_key.rs
+++ b/openssl/src/ec_key.rs
@@ -12,16 +12,7 @@ type_!(EcKey, EcKeyRef, ffi::EC_KEY, ffi::EC_KEY_free);
 
 impl EcKeyRef {
     private_key_to_pem!(ffi::PEM_write_bio_ECPrivateKey);
-
-    /// Serializes the private key components to DER.
-    pub fn private_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_ECPrivateKey(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_ECPrivateKey(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
+    private_key_to_der!(ffi::i2d_ECPrivateKey);
 }
 
 impl EcKey {
@@ -31,6 +22,7 @@ impl EcKey {
             cvt_p(ffi::EC_KEY_new_by_curve_name(nid.as_raw())).map(EcKey)
         }
     }
+
     /// Deserializes a DER-encoded private key.
     pub fn private_key_from_der(der: &[u8]) -> Result<EcKey, ErrorStack> {
         unsafe {
diff --git a/openssl/src/macros.rs b/openssl/src/macros.rs
index 0be5ff17..7fa15d1f 100644
--- a/openssl/src/macros.rs
+++ b/openssl/src/macros.rs
@@ -135,3 +135,38 @@ macro_rules! private_key_to_pem {
         }
     }
 }
+
+macro_rules! to_der_inner {
+    (#[$m:meta] $n:ident, $f:path) => {
+        #[$m]
+        pub fn $n(&self) -> Result<Vec<u8>, ::error::ErrorStack> {
+            unsafe {
+                let len = try!(::cvt($f(::types::OpenSslTypeRef::as_ptr(self), ptr::null_mut())));
+                let mut buf = vec![0; len as usize];
+                try!(::cvt($f(::types::OpenSslTypeRef::as_ptr(self), &mut buf.as_mut_ptr())));
+                Ok(buf)
+            }
+        }
+    };
+}
+
+macro_rules! to_der {
+    ($f:path) => {
+        to_der_inner!(/// Serializes this value to DER.
+            to_der, $f);
+    }
+}
+
+macro_rules! private_key_to_der {
+    ($f:path) => {
+        to_der_inner!(/// Serializes the private key to DER.
+            private_key_to_der, $f);
+    }
+}
+
+macro_rules! public_key_to_der {
+    ($f:path) => {
+        to_der_inner!(/// Serializes the public key to DER.
+            public_key_to_der, $f);
+    }
+}
diff --git a/openssl/src/pkey.rs b/openssl/src/pkey.rs
index 079a04cc..05df2f4b 100644
--- a/openssl/src/pkey.rs
+++ b/openssl/src/pkey.rs
@@ -50,6 +50,9 @@ impl PKeyRef {
 
     private_key_to_pem!(ffi::PEM_write_bio_PKCS8PrivateKey);
 
+    private_key_to_der!(ffi::i2d_PrivateKey);
+    public_key_to_der!(ffi::i2d_PUBKEY);
+
     /// Encodes the public key in the PEM format.
     pub fn public_key_to_pem(&self) -> Result<Vec<u8>, ErrorStack> {
         let mem_bio = try!(MemBio::new());
@@ -59,24 +62,6 @@ impl PKeyRef {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Encodes the public key in the DER format.
-    pub fn public_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        let mem_bio = try!(MemBio::new());
-        unsafe {
-            try!(cvt(ffi::i2d_PUBKEY_bio(mem_bio.as_ptr(), self.as_ptr())));
-        }
-        Ok(mem_bio.get_buf().to_owned())
-    }
-
-    /// Encodes the private key in the DER format
-    pub fn private_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        let mem_bio = try!(MemBio::new());
-        unsafe {
-            try!(cvt(ffi::i2d_PrivateKey_bio(mem_bio.as_ptr(), self.as_ptr())));
-        }
-        Ok(mem_bio.get_buf().to_owned())
-    }
-
     /// Returns the size of the key.
     ///
     /// This corresponds to the bit length of the modulus of an RSA key, and the bit length of the
diff --git a/openssl/src/rsa.rs b/openssl/src/rsa.rs
index f2dd8d00..89c0bb85 100644
--- a/openssl/src/rsa.rs
+++ b/openssl/src/rsa.rs
@@ -36,25 +36,8 @@ impl RsaRef {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Encodes an RSA private key as unencrypted DER formatted data.
-    pub fn private_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_RSAPrivateKey(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_RSAPrivateKey(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
-
-    /// Encodes an RSA public key as DER formatted data.
-    pub fn public_key_to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        unsafe {
-            let len = try!(cvt(ffi::i2d_RSA_PUBKEY(self.as_ptr(), ptr::null_mut())));
-            let mut buf = vec![0; len as usize];
-            try!(cvt(ffi::i2d_RSA_PUBKEY(self.as_ptr(), &mut buf.as_mut_ptr())));
-            Ok(buf)
-        }
-    }
+    private_key_to_der!(ffi::i2d_RSAPrivateKey);
+    public_key_to_der!(ffi::i2d_RSA_PUBKEY);
 
     // FIXME should return u32
     pub fn size(&self) -> usize {
diff --git a/openssl/src/x509/mod.rs b/openssl/src/x509/mod.rs
index e7c633d0..74f586c2 100644
--- a/openssl/src/x509/mod.rs
+++ b/openssl/src/x509/mod.rs
@@ -425,14 +425,7 @@ impl X509Ref {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Returns a DER serialized form of the certificate
-    pub fn to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        let mem_bio = try!(MemBio::new());
-        unsafe {
-            ffi::i2d_X509_bio(mem_bio.as_ptr(), self.as_ptr());
-        }
-        Ok(mem_bio.get_buf().to_owned())
-    }
+    to_der!(ffi::i2d_X509);
 }
 
 impl ToOwned for X509Ref {
@@ -575,14 +568,7 @@ impl X509ReqRef {
         Ok(mem_bio.get_buf().to_owned())
     }
 
-    /// Returns a DER serialized form of the CSR
-    pub fn to_der(&self) -> Result<Vec<u8>, ErrorStack> {
-        let mem_bio = try!(MemBio::new());
-        unsafe {
-            ffi::i2d_X509_REQ_bio(mem_bio.as_ptr(), self.as_ptr());
-        }
-        Ok(mem_bio.get_buf().to_owned())
-    }
+    to_der!(ffi::i2d_X509_REQ);
 }
 
 impl X509Req {