diff --git a/ChangeLog b/ChangeLog
index a64de5d..d33897c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,12 @@
    * Wipe stack buffers in RSA private key operations
      (rsa_rsaes_pkcs1_v15_decrypt(), rsa_rsaes_oaep_decrypt).
      Found by Laurent Simon.
+   * Accept empty trusted CA chain in authentication mode
+     SSL_VERIFY_OPTIONAL. Fixes #864. Found by jethrogb.
+   * Fix implementation of ssl_parse_certificate
+     to not annihilate fatal errors in authentication mode
+     SSL_VERIFY_OPTIONAL and to reflect bad EC curves
+     within verification result.
 
 = mbed TLS 1.3.19 branch released 2017-03-08
 
diff --git a/include/polarssl/x509.h b/include/polarssl/x509.h
index cd01539..adaacff 100644
--- a/include/polarssl/x509.h
+++ b/include/polarssl/x509.h
@@ -97,6 +97,8 @@
 #define BADCERT_KEY_USAGE         0x0800  /**< Usage does not match the keyUsage extension. */
 #define BADCERT_EXT_KEY_USAGE     0x1000  /**< Usage does not match the extendedKeyUsage extension. */
 #define BADCERT_NS_CERT_TYPE      0x2000  /**< Usage does not match the nsCertType extension. */
+#define BADCERT_BAD_KEY          0x10000  /**< Bad key (e.g. unsupported elliptic curve in use) */
+
 /* \} name */
 /* \} addtogroup x509_module */
 
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 7cf968d..5779229 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2841,12 +2841,6 @@
 
     if( ssl->authmode != SSL_VERIFY_NONE )
     {
-        if( ssl->ca_chain == NULL )
-        {
-            SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
-            return( POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED );
-        }
-
         /*
          * Main check: verify certificate
          */
@@ -2872,6 +2866,8 @@
             if( pk_can_do( pk, POLARSSL_PK_ECKEY ) &&
                 ! ssl_curve_is_acceptable( ssl, pk_ec( *pk )->grp.id ) )
             {
+                ssl->session_negotiate->verify_result |= BADCERT_BAD_KEY;
+
                 SSL_DEBUG_MSG( 1, ( "bad certificate (EC key curve)" ) );
                 if( ret == 0 )
                     ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
@@ -2889,8 +2885,36 @@
                 ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
         }
 
-        if( ssl->authmode != SSL_VERIFY_REQUIRED )
+        /* x509_crt_verify_with_profile is supposed to report a
+         * verification failure through POLARSSL_ERR_X509_CERT_VERIFY_FAILED,
+         * with details encoded in the verification flags. All other kinds
+         * of error codes, including those from the user provided f_vrfy
+         * functions, are treated as fatal and lead to a failure of
+         * ssl_parse_certificate even if verification was optional. */
+        if( ssl->authmode == SSL_VERIFY_OPTIONAL &&
+            ( ret == POLARSSL_ERR_X509_CERT_VERIFY_FAILED ||
+              ret == POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE ) )
+        {
             ret = 0;
+        }
+
+        if( ssl->ca_chain == NULL && ssl->authmode == SSL_VERIFY_REQUIRED )
+        {
+            SSL_DEBUG_MSG( 1, ( "got no CA chain" ) );
+            ret = POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED;
+        }
+
+#if defined(POLARSSL_DEBUG_C)
+        if( ssl->session_negotiate->verify_result != 0 )
+        {
+            SSL_DEBUG_MSG( 3, ( "! Certificate verification flags %x",
+                                ssl->session_negotiate->verify_result ) );
+        }
+        else
+        {
+            SSL_DEBUG_MSG( 3, ( "Certificate verification flags clear" ) );
+        }
+#endif /* POLARSSL_DEBUG_C */
     }
 
     SSL_DEBUG_MSG( 2, ( "<= parse certificate" ) );
diff --git a/library/x509_crt.c b/library/x509_crt.c
index a3517f6..16a29b5 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1403,6 +1403,7 @@
     { BADCERT_KEY_USAGE,     "Usage does not match the keyUsage extension" },
     { BADCERT_EXT_KEY_USAGE, "Usage does not match the extendedKeyUsage extension" },
     { BADCERT_NS_CERT_TYPE,  "Usage does not match the nsCertType extension" },
+    { BADCERT_BAD_KEY,       "The certificate uses an invalid key (e.g. unsupported elliptic curve)" },
     { 0, NULL }
 };