diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index fb8c23fee..1e58ca3eb 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -945,6 +945,8 @@ static inline int mbedtls_ssl_get_psk( const mbedtls_ssl_context *ssl,
 
     else
     {
+        *psk = NULL;
+        *psk_len = 0;
         return( MBEDTLS_ERR_SSL_PRIVATE_KEY_REQUIRED );
     }
 
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6dabd3409..4a8686cc4 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1848,7 +1848,7 @@ int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exch
 {
     unsigned char *p = ssl->handshake->premaster;
     unsigned char *end = p + sizeof( ssl->handshake->premaster );
-    const unsigned char *psk;
+    const unsigned char *psk = NULL;
     size_t psk_len = 0;
 
     if( mbedtls_ssl_get_psk( ssl, &psk, &psk_len )