diff --git a/crypto/openssl_mbedtls_wrapper/mbedtls/err.c b/crypto/openssl_mbedtls_wrapper/mbedtls/err.c
index d69459217a..0332253d4d 100644
--- a/crypto/openssl_mbedtls_wrapper/mbedtls/err.c
+++ b/crypto/openssl_mbedtls_wrapper/mbedtls/err.c
@@ -31,7 +31,7 @@
  * Public Functions
  ****************************************************************************/
 
-unsigned long ERR_peek_last_error()
+unsigned long ERR_peek_last_error(void)
 {
   return errno;
 }
diff --git a/crypto/openssl_mbedtls_wrapper/mbedtls/hmac.c b/crypto/openssl_mbedtls_wrapper/mbedtls/hmac.c
index 0b16617fdb..1e962d1b5d 100644
--- a/crypto/openssl_mbedtls_wrapper/mbedtls/hmac.c
+++ b/crypto/openssl_mbedtls_wrapper/mbedtls/hmac.c
@@ -132,35 +132,35 @@ size_t EVP_MD_size(const EVP_MD *md)
   return mbedtls_md_get_size((const mbedtls_md_info_t *)md);
 }
 
-const EVP_MD *EVP_sha1()
+const EVP_MD *EVP_sha1(void)
 {
   const mbedtls_md_info_t *md_info =
     mbedtls_md_info_from_type(MBEDTLS_MD_SHA1);
   return (const EVP_MD *)md_info;
 }
 
-const EVP_MD *EVP_sha224()
+const EVP_MD *EVP_sha224(void)
 {
   const mbedtls_md_info_t *md_info =
     mbedtls_md_info_from_type(MBEDTLS_MD_SHA224);
   return (const EVP_MD *)md_info;
 }
 
-const EVP_MD *EVP_sha256()
+const EVP_MD *EVP_sha256(void)
 {
   const mbedtls_md_info_t *md_info =
     mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
   return (const EVP_MD *)md_info;
 }
 
-const EVP_MD *EVP_sha384()
+const EVP_MD *EVP_sha384(void)
 {
   const mbedtls_md_info_t *md_info =
     mbedtls_md_info_from_type(MBEDTLS_MD_SHA384);
   return (const EVP_MD *)md_info;
 }
 
-const EVP_MD *EVP_sha512()
+const EVP_MD *EVP_sha512(void)
 {
   const mbedtls_md_info_t *md_info =
     mbedtls_md_info_from_type(MBEDTLS_MD_SHA512);