diff --git a/ext/puma_http11/mini_ssl.c b/ext/puma_http11/mini_ssl.c
index 2d22be2395..85d7054067 100644
--- a/ext/puma_http11/mini_ssl.c
+++ b/ext/puma_http11/mini_ssl.c
@@ -49,7 +49,7 @@ const rb_data_type_t engine_data_type = {
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY,
 };
 
-DH *get_dh2048() {
+DH *get_dh2048(void) {
   /* `openssl dhparam -C 2048`
    * -----BEGIN DH PARAMETERS-----
    * MIIBCAKCAQEAjmh1uQHdTfxOyxEbKAV30fUfzqMDF/ChPzjfyzl2jcrqQMhrk76o
diff --git a/ext/puma_http11/puma_http11.c b/ext/puma_http11/puma_http11.c
index 6520f5c393..19242dd4c1 100644
--- a/ext/puma_http11/puma_http11.c
+++ b/ext/puma_http11/puma_http11.c
@@ -451,7 +451,7 @@ VALUE HttpParser_body(VALUE self) {
 void Init_mini_ssl(VALUE mod);
 #endif
 
-void Init_puma_http11()
+void Init_puma_http11(void)
 {
 
   VALUE mPuma = rb_define_module("Puma");