diff --git a/crypto/evp/evp.c b/crypto/evp/evp.c
index 06fdabf..c7c4ffb 100644
--- a/crypto/evp/evp.c
+++ b/crypto/evp/evp.c
@@ -74,7 +74,7 @@
 extern const EVP_PKEY_ASN1_METHOD hmac_asn1_meth;
 extern const EVP_PKEY_ASN1_METHOD rsa_asn1_meth;
 
-EVP_PKEY *EVP_PKEY_new() {
+EVP_PKEY *EVP_PKEY_new(void) {
   EVP_PKEY *ret;
 
   ret = OPENSSL_malloc(sizeof(EVP_PKEY));
@@ -427,6 +427,6 @@
                            0, (void *)out_md);
 }
 
-void OpenSSL_add_all_algorithms() {}
+void OpenSSL_add_all_algorithms(void) {}
 
-void EVP_cleanup() {}
+void EVP_cleanup(void) {}
diff --git a/crypto/evp/example_sign.c b/crypto/evp/example_sign.c
index df7156b..847330d 100644
--- a/crypto/evp/example_sign.c
+++ b/crypto/evp/example_sign.c
@@ -95,7 +95,7 @@
 };
 
 
-int example_EVP_DigestSignInit() {
+int example_EVP_DigestSignInit(void) {
   int ret = 0;
   EVP_PKEY *pkey = NULL;
   RSA *rsa = NULL;
@@ -154,7 +154,7 @@
   return ret;
 }
 
-int example_EVP_DigestVerifyInit() {
+int example_EVP_DigestVerifyInit(void) {
   int ret = 0;
   EVP_PKEY *pkey = NULL;
   RSA *rsa = NULL;
@@ -193,7 +193,7 @@
   return ret;
 }
 
-int main() {
+int main(void) {
   if (!example_EVP_DigestSignInit()) {
     fprintf(stderr, "EVP_DigestSignInit failed\n");
     return 1;