diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index 1597478..a063695 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -395,19 +395,19 @@
 int x509write_pubkey_der( pk_context *key, unsigned char *buf, size_t size );
 
 /**
- * \brief           Write a RSA key to a PKCS#1 DER structure
+ * \brief           Write a private key to a PKCS#1 or SEC1 DER structure
  *                  Note: data is written at the end of the buffer! Use the
  *                        return value to determine where you should start
  *                        using the buffer
  *
- * \param rsa       RSA to write away
+ * \param key       private to write away
  * \param buf       buffer to write to
  * \param size      size of the buffer
  *
  * \return          length of data written if successful, or a specific
  *                  error code
  */
-int x509write_key_der( rsa_context *rsa, unsigned char *buf, size_t size );
+int x509write_key_der( pk_context *pk, unsigned char *buf, size_t size );
 
 /**
  * \brief           Write a CSR (Certificate Signing Request) to a
@@ -458,15 +458,15 @@
 int x509write_pubkey_pem( pk_context *key, unsigned char *buf, size_t size );
 
 /**
- * \brief           Write a RSA key to a PKCS#1 PEM string
+ * \brief           Write a private key to a PKCS#1 or SEC1 PEM string
  *
- * \param rsa       RSA to write away
+ * \param key       private to write away
  * \param buf       buffer to write to
  * \param size      size of the buffer
  *
  * \return          0 successful, or a specific error code
  */
-int x509write_key_pem( rsa_context *rsa, unsigned char *buf, size_t size );
+int x509write_key_pem( pk_context *key, unsigned char *buf, size_t size );
 
 /**
  * \brief           Write a CSR (Certificate Signing Request) to a
diff --git a/library/x509parse.c b/library/x509parse.c
index fc84e61..b3725a7 100644
--- a/library/x509parse.c
+++ b/library/x509parse.c
@@ -2521,7 +2521,7 @@
     unsigned char *end2;
 
     /*
-     * RFC 5915, orf SEC1 Appendix C.4
+     * RFC 5915, or SEC1 Appendix C.4
      *
      * ECPrivateKey ::= SEQUENCE {
      *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
diff --git a/library/x509write.c b/library/x509write.c
index 937b899..d55e241 100644
--- a/library/x509write.c
+++ b/library/x509write.c
@@ -542,26 +542,86 @@
     return( len );
 }
 
-int x509write_key_der( rsa_context *rsa, unsigned char *buf, size_t size )
+int x509write_key_der( pk_context *key, unsigned char *buf, size_t size )
 {
     int ret;
-    unsigned char *c;
+    unsigned char *c = buf + size;
     size_t len = 0;
 
-    c = buf + size;
+#if defined(POLARSSL_RSA_C)
+    if( pk_get_type( key ) == POLARSSL_PK_RSA )
+    {
+        rsa_context *rsa = pk_rsa( *key );
 
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->QP ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DQ ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DP ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->Q ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->P ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->D ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
-    ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );
-    ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 0 ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->QP ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DQ ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DP ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->Q ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->P ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->D ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );
+        ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 0 ) );
 
-    ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
-    ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+        ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
+        ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+    }
+    else
+#endif
+#if defined(POLARSSL_ECP_C)
+    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
+    {
+        ecp_keypair *ec = pk_ec( *key );
+        size_t pub_len = 0, par_len = 0;
+
+        /*
+         * RFC 5915, or SEC1 Appendix C.4
+         *
+         * ECPrivateKey ::= SEQUENCE {
+         *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
+         *      privateKey     OCTET STRING,
+         *      parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
+         *      publicKey  [1] BIT STRING OPTIONAL
+         *    }
+         */
+
+        /* publicKey */
+        ASN1_CHK_ADD( pub_len, x509_write_ec_pubkey( &c, buf, ec ) );
+
+        if( c - buf < 1 )
+            return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
+        *--c = 0;
+        pub_len += 1;
+
+        ASN1_CHK_ADD( pub_len, asn1_write_len( &c, buf, pub_len ) );
+        ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, buf, ASN1_BIT_STRING ) );
+
+        ASN1_CHK_ADD( pub_len, asn1_write_len( &c, buf, pub_len ) );
+        ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, buf,
+                            ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 1 ) );
+        len += pub_len;
+
+        /* parameters */
+        ASN1_CHK_ADD( par_len, x509_write_ec_param( &c, buf, ec ) );
+
+        ASN1_CHK_ADD( par_len, asn1_write_len( &c, buf, par_len ) );
+        ASN1_CHK_ADD( par_len, asn1_write_tag( &c, buf,
+                            ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 0 ) );
+        len += par_len;
+
+        /* privateKey: write as MPI then fix tag */
+        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &ec->d ) );
+        *c = ASN1_OCTET_STRING;
+
+        /* version */
+        ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 1 ) );
+
+        ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
+        ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+    }
+    else
+#endif
+        return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
 
     return( len );
 }
@@ -957,8 +1017,10 @@
 #define PEM_BEGIN_PUBLIC_KEY    "-----BEGIN PUBLIC KEY-----\n"
 #define PEM_END_PUBLIC_KEY      "-----END PUBLIC KEY-----\n"
 
-#define PEM_BEGIN_PRIVATE_KEY   "-----BEGIN RSA PRIVATE KEY-----\n"
-#define PEM_END_PRIVATE_KEY     "-----END RSA PRIVATE KEY-----\n"
+#define PEM_BEGIN_PRIVATE_KEY_RSA   "-----BEGIN RSA PRIVATE KEY-----\n"
+#define PEM_END_PRIVATE_KEY_RSA     "-----END RSA PRIVATE KEY-----\n"
+#define PEM_BEGIN_PRIVATE_KEY_EC    "-----BEGIN EC PRIVATE KEY-----\n"
+#define PEM_END_PRIVATE_KEY_EC      "-----END EC PRIVATE KEY-----\n"
 
 #if defined(POLARSSL_BASE64_C)
 static int x509write_pemify( const char *begin_str, const char *end_str,
@@ -1042,18 +1104,37 @@
     return( 0 );
 }
 
-int x509write_key_pem( rsa_context *rsa, unsigned char *buf, size_t size )
+int x509write_key_pem( pk_context *key, unsigned char *buf, size_t size )
 {
     int ret;
     unsigned char output_buf[4096];
+    char *begin, *end;
 
-    if( ( ret = x509write_key_der( rsa, output_buf,
+    if( ( ret = x509write_key_der( key, output_buf,
                                       sizeof(output_buf) ) ) < 0 )
     {
         return( ret );
     }
 
-    if( ( ret = x509write_pemify( PEM_BEGIN_PRIVATE_KEY, PEM_END_PRIVATE_KEY,
+#if defined(POLARSSL_RSA_C)
+    if( pk_get_type( key ) == POLARSSL_PK_RSA )
+    {
+        begin = PEM_BEGIN_PRIVATE_KEY_RSA;
+        end = PEM_END_PRIVATE_KEY_RSA;
+    }
+    else
+#endif
+#if defined(POLARSSL_ECP_C)
+    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
+    {
+        begin = PEM_BEGIN_PRIVATE_KEY_EC;
+        end = PEM_END_PRIVATE_KEY_EC;
+    }
+    else
+#endif
+        return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
+
+    if( ( ret = x509write_pemify( begin, end,
                                   output_buf + sizeof(output_buf) - ret,
                                   ret, buf, size ) ) != 0 )
     {
diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index 1393103..c2d4e4e 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -169,7 +169,7 @@
     pk_init( &key );
     TEST_ASSERT( x509parse_keyfile( &key, key_file, NULL ) == 0 );
 
-    ret = x509write_key_pem( pk_rsa( key ), buf, sizeof( buf ) - 1);
+    ret = x509write_key_pem( &key, buf, sizeof( buf ) - 1);
     TEST_ASSERT( ret >= 0 );
 
     f = fopen( key_file, "r" );