diff --git a/shim/shim.h b/shim/shim.h
index 5f5f8fb..9c383b6 100644
--- a/shim/shim.h
+++ b/shim/shim.h
@@ -9,28 +9,28 @@
 #include <OpenSSL/cms.h>
 
 #undef SSL_library_init
-static inline void SSL_library_init() {
+static inline void SSL_library_init(void) {
     OPENSSL_init_ssl(0, NULL);
 }
 
 #undef SSL_load_error_strings
-static inline void SSL_load_error_strings() {
+static inline void SSL_load_error_strings(void) {
     OPENSSL_init_ssl(OPENSSL_INIT_LOAD_SSL_STRINGS \
                      | OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);
 }
 
 #undef OpenSSL_add_all_ciphers
-static inline void OpenSSL_add_all_ciphers() {
+static inline void OpenSSL_add_all_ciphers(void) {
     OPENSSL_init_crypto(OPENSSL_INIT_ADD_ALL_CIPHERS, NULL);
 }
 
 #undef OpenSSL_add_all_digests
-static inline void OpenSSL_add_all_digests() {
+static inline void OpenSSL_add_all_digests(void) {
     OPENSSL_init_crypto(OPENSSL_INIT_ADD_ALL_DIGESTS, NULL);
 }
 
 #undef OpenSSL_add_all_algorithms
-static inline void OpenSSL_add_all_algorithms() {
+static inline void OpenSSL_add_all_algorithms(void) {
     #ifdef OPENSSL_LOAD_CONF
     OPENSSL_add_all_algorithms_conf();
     #else