diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 6591ecb..f61c634 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -680,11 +680,13 @@
 
     *olen = 0;
 
+    int not_using_psk = 0;
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
-    if( mbedtls_svc_key_id_is_null( ssl->handshake->psk_opaque ) )
+    not_using_psk = ( mbedtls_svc_key_id_is_null( ssl->handshake->psk_opaque ) );
 #else
-    if( ssl->handshake->psk == NULL )
+    not_using_psk = ( ssl->handshake->psk == NULL );
 #endif
+    if( not_using_psk )
     {
         /* We shouldn't have called this extension writer unless we've
          * chosen to use a PSK. */