diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index fb8c23f..1e58ca3 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -945,6 +945,8 @@
 
     else
     {
+        *psk = NULL;
+        *psk_len = 0;
         return( MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED );
     }