diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 6fe8cae..f5ef920 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -92,8 +92,9 @@
         return;
     }
 
-    MBEDTLS_SSL_DEBUG_MSG(2, ("No matched ciphersuite, psk_ciphersuite_id=%x, psk_hash_alg=%x",
-                              (unsigned) psk_ciphersuite_id, psk_hash_alg));
+    MBEDTLS_SSL_DEBUG_MSG(2, ("No matched ciphersuite, psk_ciphersuite_id=%x, psk_hash_alg=%lx",
+                              (unsigned) psk_ciphersuite_id,
+                              (unsigned long) psk_hash_alg));
 }
 
 #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED)