diff --git a/programs/hash/md_hmac_demo.c b/programs/hash/md_hmac_demo.c
index 581816a..a0127ed 100644
--- a/programs/hash/md_hmac_demo.c
+++ b/programs/hash/md_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>
 
@@ -56,16 +58,6 @@
  * 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, unsigned char *buf, size_t len)
-{
-    printf("%s:", title);
-    for (size_t i = 0; i < len; i++) {
-        printf(" %02x", buf[i]);
-    }
-    printf("\n");
-}
-
 /* Run an Mbed TLS function and bail out if it fails.
  * A string description of the error code can be recovered with:
  * programs/util/strerror <value> */
@@ -107,14 +99,14 @@
     CHK(mbedtls_md_hmac_update(&ctx, msg1_part1, sizeof(msg1_part1)));
     CHK(mbedtls_md_hmac_update(&ctx, msg1_part2, sizeof(msg1_part2)));
     CHK(mbedtls_md_hmac_finish(&ctx, out));
-    print_buf("msg1", out, mbedtls_md_get_size(info));
+    mbedtls_test_print_buf("msg1", out, mbedtls_md_get_size(info));
 
     /* compute HMAC(key, msg2_part1 | msg2_part2) */
     CHK(mbedtls_md_hmac_reset(&ctx));     // prepare for new operation
     CHK(mbedtls_md_hmac_update(&ctx, msg2_part1, sizeof(msg2_part1)));
     CHK(mbedtls_md_hmac_update(&ctx, msg2_part2, sizeof(msg2_part2)));
     CHK(mbedtls_md_hmac_finish(&ctx, out));
-    print_buf("msg2", out, mbedtls_md_get_size(info));
+    mbedtls_test_print_buf("msg2", out, mbedtls_md_get_size(info));
 
 exit:
     mbedtls_md_free(&ctx);