diff --git a/programs/hash/md_hmac_demo.c b/programs/hash/md_hmac_demo.c
index a0127ed..ba51bfd 100644
--- a/programs/hash/md_hmac_demo.c
+++ b/programs/hash/md_hmac_demo.c
@@ -79,7 +79,7 @@
  * This function demonstrates computation of the HMAC of two messages using
  * the multipart API.
  */
-int hmac_demo(void)
+static int hmac_demo(void)
 {
     int ret;
     const mbedtls_md_type_t alg = MBEDTLS_MD_SHA256;