diff --git a/ChangeLog b/ChangeLog
index c6f8a7ede..ac33f5bf9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,9 @@ mbed TLS ChangeLog (Sorted per branch, date)
 = mbed TLS 2.1.3 released 2015-10-xx
 
 Security
+   * Fix potential double free if mbedtls_ssl_conf_psk() is called more than
+     once and some allocation fails. Cannot be forced remotely. Found by Guido
+     Vranken, Intelworks.
    * The X509 max_pathlen constraint was not enforced on intermediate
      certificates. Found by Nicholas Wilson, fix and tests provided by
      Janos Follath. #280 and #319
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index bc1783375..379cce135 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5725,6 +5725,8 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
     {
         mbedtls_free( conf->psk );
         mbedtls_free( conf->psk_identity );
+        conf->psk = NULL;
+        conf->psk_identity = NULL;
     }
 
     if( ( conf->psk = mbedtls_calloc( 1, psk_len ) ) == NULL ||