diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index bf49af2..bbc8535 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -106,7 +106,7 @@
 static int ssl_tls13_offered_psks_check_identity_match(
                mbedtls_ssl_context *ssl,
                const unsigned char *identity,
-               uint16_t identity_len )
+               size_t identity_len )
 {
     /* Check identity with external configured function */
     if( ssl->conf->f_psk != NULL )
@@ -121,7 +121,8 @@
 
     MBEDTLS_SSL_DEBUG_BUF( 5, "identity", identity, identity_len );
     /* Check identity with pre-configured psk */
-    if( identity_len == ssl->conf->psk_identity_len &&
+    if( ssl->conf->psk_identity != NULL &&
+        identity_len == ssl->conf->psk_identity_len &&
         mbedtls_ct_memcmp( ssl->conf->psk_identity,
                             identity, identity_len ) == 0 )
     {
@@ -134,7 +135,7 @@
 
 MBEDTLS_CHECK_RETURN_CRITICAL
 static int ssl_tls13_get_psk( mbedtls_ssl_context *ssl,
-                              const unsigned char **psk,
+                              unsigned char **psk,
                               size_t *psk_len )
 {
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
@@ -150,7 +151,7 @@
         return( psa_ssl_status_to_mbedtls( status ) );
     }
 
-    *psk_len = PSA_BITS_TO_BYTES(psa_get_key_bits( &key_attributes ) );
+    *psk_len = PSA_BITS_TO_BYTES( psa_get_key_bits( &key_attributes ) );
     *psk = mbedtls_calloc( 1, *psk_len );
     if( *psk == NULL )
     {
@@ -174,22 +175,32 @@
 MBEDTLS_CHECK_RETURN_CRITICAL
 static int ssl_tls13_offered_psks_check_binder_match( mbedtls_ssl_context *ssl,
                                                       const unsigned char *binder,
-                                                      uint16_t binder_len )
+                                                      size_t binder_len )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     int psk_type;
 
-    mbedtls_md_type_t md_alg =
-        binder_len == 32 ? MBEDTLS_MD_SHA256 : MBEDTLS_MD_SHA384 ;
-    psa_algorithm_t psa_md_alg = mbedtls_psa_translate_md( md_alg );
+    mbedtls_md_type_t md_alg;
+    psa_algorithm_t psa_md_alg;
     unsigned char transcript[PSA_HASH_MAX_SIZE];
     size_t transcript_len;
-    const unsigned char *psk;
+    unsigned char *psk;
     size_t psk_len;
     unsigned char server_computed_binder[PSA_HASH_MAX_SIZE];
 
     psk_type = MBEDTLS_SSL_TLS1_3_PSK_EXTERNAL;
-
+    switch( binder_len )
+    {
+    case 32:
+        md_alg = MBEDTLS_MD_SHA256;
+        break;
+    case 48:
+        md_alg = MBEDTLS_MD_SHA384;
+        break;
+    default:
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+    psa_md_alg = mbedtls_psa_translate_md( md_alg );
     /* Get current state of handshake transcript. */
     ret = mbedtls_ssl_get_handshake_transcript( ssl, md_alg,
                                                 transcript, sizeof( transcript ),
@@ -215,7 +226,7 @@
     }
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder ( computed ): ",
-                           server_computed_binder, binder_len );
+                           server_computed_binder, transcript_len );
     MBEDTLS_SSL_DEBUG_BUF( 3, "psk binder ( received ): ", binder, binder_len );
 
     if( mbedtls_ct_memcmp( server_computed_binder, binder, binder_len ) == 0 )
@@ -262,7 +273,7 @@
     int matched_identity = -1;
     int identity_id = -1;
 
-    MBEDTLS_SSL_DEBUG_BUF( 3, "pre_shared_key extesion", buf, end - buf );
+    MBEDTLS_SSL_DEBUG_BUF( 3, "pre_shared_key extension", buf, end - buf );
 
     /* identities_len       2 bytes
      * identities_data   >= 7 bytes