diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 672cb0f..183b6ee 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -2036,8 +2036,12 @@
 
     psa_hash_alg = mbedtls_psa_translate_md( ciphersuite_info->mac );
     hash_length = PSA_HASH_LENGTH( psa_hash_alg );
-    if( hash_length == -1 )
+    if( hash_length == -1 ||
+        ( size_t )hash_length > sizeof( session->resumption_key ) )
+    {
         return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "resumption_master_secret",
                            session->app_secrets.resumption_master_secret,