diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 9142be8..991be17 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5701,6 +5701,8 @@
     {
         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 ||