diff --git a/programs/psa/hmac_demo.c b/programs/psa/hmac_demo.c
index 2055054..6ed8298 100644
--- a/programs/psa/hmac_demo.c
+++ b/programs/psa/hmac_demo.c
@@ -32,6 +32,8 @@
 
 #include "mbedtls/platform_util.h" // for mbedtls_platform_zeroize
 
+#include <test/helpers.h>
+
 #include <stdlib.h>
 #include <stdio.h>
 
@@ -58,16 +60,6 @@
  * This example program uses SHA-256, so a 32-byte key makes sense. */
 const unsigned char key_bytes[32] = { 0 };
 
-/* Print the contents of a buffer in hex */
-void print_buf(const char *title, uint8_t *buf, size_t len)
-{
-    printf("%s:", title);
-    for (size_t i = 0; i < len; i++) {
-        printf(" %02x", buf[i]);
-    }
-    printf("\n");
-}
-
 /* Run a PSA function and bail out if it fails.
  * The symbolic name of the error code can be recovered using:
  * programs/psa/psa_constant_name status <value> */
@@ -122,14 +114,14 @@
     PSA_CHECK(psa_mac_update(&op, msg1_part1, sizeof(msg1_part1)));
     PSA_CHECK(psa_mac_update(&op, msg1_part2, sizeof(msg1_part2)));
     PSA_CHECK(psa_mac_sign_finish(&op, out, sizeof(out), &out_len));
-    print_buf("msg1", out, out_len);
+    mbedtls_test_print_buf("msg1", out, out_len);
 
     /* compute HMAC(key, msg2_part1 | msg2_part2) */
     PSA_CHECK(psa_mac_sign_setup(&op, key, alg));
     PSA_CHECK(psa_mac_update(&op, msg2_part1, sizeof(msg2_part1)));
     PSA_CHECK(psa_mac_update(&op, msg2_part2, sizeof(msg2_part2)));
     PSA_CHECK(psa_mac_sign_finish(&op, out, sizeof(out), &out_len));
-    print_buf("msg2", out, out_len);
+    mbedtls_test_print_buf("msg2", out, out_len);
 
 exit:
     psa_mac_abort(&op);   // needed on error, harmless on success