diff --git a/mongoose.c b/mongoose.c
index 0be691e2..6349adc1 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -4679,7 +4679,7 @@ struct mg_ssl_if_ctx {
   size_t identity_len;
 };
 
-void mg_ssl_if_init() {
+void mg_ssl_if_init(void) {
   SSL_library_init();
 }
 
@@ -5110,7 +5110,7 @@ struct mg_ssl_if_ctx {
 /* Must be provided by the platform. ctx is struct mg_connection. */
 extern int mg_ssl_if_mbed_random(void *ctx, unsigned char *buf, size_t len);
 
-void mg_ssl_if_init() {
+void mg_ssl_if_init(void) {
   LOG(LL_INFO, ("%s", MBEDTLS_VERSION_STRING_FULL));
 }
 
diff --git a/mongoose.h b/mongoose.h
index 598e9974..03d128d0 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -3844,7 +3844,7 @@ extern "C" {
 struct mg_ssl_if_ctx;
 struct mg_connection;
 
-void mg_ssl_if_init();
+void mg_ssl_if_init(void);
 
 enum mg_ssl_if_result {
   MG_SSL_OK = 0,
diff --git a/src/mg_ssl_if.h b/src/mg_ssl_if.h
index 62f24b51..0ccd3f0a 100644
--- a/src/mg_ssl_if.h
+++ b/src/mg_ssl_if.h
@@ -15,7 +15,7 @@ extern "C" {
 struct mg_ssl_if_ctx;
 struct mg_connection;
 
-void mg_ssl_if_init();
+void mg_ssl_if_init(void);
 
 enum mg_ssl_if_result {
   MG_SSL_OK = 0,
diff --git a/src/mg_ssl_if_mbedtls.c b/src/mg_ssl_if_mbedtls.c
index 7640778f..a4508ace 100644
--- a/src/mg_ssl_if_mbedtls.c
+++ b/src/mg_ssl_if_mbedtls.c
@@ -52,7 +52,7 @@ struct mg_ssl_if_ctx {
 /* Must be provided by the platform. ctx is struct mg_connection. */
 extern int mg_ssl_if_mbed_random(void *ctx, unsigned char *buf, size_t len);
 
-void mg_ssl_if_init() {
+void mg_ssl_if_init(void) {
   LOG(LL_INFO, ("%s", MBEDTLS_VERSION_STRING_FULL));
 }
 
diff --git a/src/mg_ssl_if_openssl.c b/src/mg_ssl_if_openssl.c
index 98af8e29..c29a5448 100644
--- a/src/mg_ssl_if_openssl.c
+++ b/src/mg_ssl_if_openssl.c
@@ -21,7 +21,7 @@ struct mg_ssl_if_ctx {
   size_t identity_len;
 };
 
-void mg_ssl_if_init() {
+void mg_ssl_if_init(void) {
   SSL_library_init();
 }