diff --git a/test/dtls_mtu_test.c b/test/dtls_mtu_test.c
index df1013ac51ad4fe0242eb1b0636fe89d9087d7b3..da970a7fa7151d508836bcfbe15612f9efb43784 100644
--- a/test/dtls_mtu_test.c
+++ b/test/dtls_mtu_test.c
@@ -26,7 +26,7 @@ static unsigned int clnt_psk_callback(SSL *ssl, const char *hint,
                                       unsigned char *psk,
                                       unsigned int max_psk_len)
 {
-    snprintf(ident, max_ident_len, "psk");
+    BIO_snprintf(ident, max_ident_len, "psk");
 
     if (max_psk_len > 20)
         max_psk_len = 20;