diff --git a/programs/fuzz/common.c b/programs/fuzz/common.c
index 75021bb..98aa403 100644
--- a/programs/fuzz/common.c
+++ b/programs/fuzz/common.c
@@ -13,7 +13,7 @@
 }
 #endif
 
-void dummy_init()
+void dummy_init(void)
 {
 #if defined(MBEDTLS_PLATFORM_TIME_ALT)
     mbedtls_platform_set_time(dummy_constant_time);
diff --git a/programs/fuzz/common.h b/programs/fuzz/common.h
index bc817bd..094383c 100644
--- a/programs/fuzz/common.h
+++ b/programs/fuzz/common.h
@@ -15,7 +15,7 @@
 #if defined(MBEDTLS_HAVE_TIME)
 mbedtls_time_t dummy_constant_time(mbedtls_time_t *time);
 #endif
-void dummy_init();
+void dummy_init(void);
 
 int dummy_send(void *ctx, const unsigned char *buf, size_t len);
 int fuzz_recv(void *ctx, unsigned char *buf, size_t len);
diff --git a/programs/ssl/ssl_context_info.c b/programs/ssl/ssl_context_info.c
index a5f0650..855b091 100644
--- a/programs/ssl/ssl_context_info.c
+++ b/programs/ssl/ssl_context_info.c
@@ -125,12 +125,12 @@
 /*
  * Basic printing functions
  */
-void print_version()
+void print_version(void)
 {
     printf("%s v%d.%d\n", PROG_NAME, VER_MAJOR, VER_MINOR);
 }
 
-void print_usage()
+void print_usage(void)
 {
     print_version();
     printf("\nThis program is used to deserialize an Mbed TLS SSL session from the base64 code provided\n"
@@ -179,7 +179,7 @@
 /*
  * Exit from the program in case of error
  */
-void error_exit()
+void error_exit(void)
 {
     if (NULL != b64_file) {
         fclose(b64_file);
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index ac527f2..685e336 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -644,7 +644,7 @@
     memcpy(&prev[prev_len++], delay, sizeof(packet));
 }
 
-int send_delayed()
+int send_delayed(void)
 {
     uint8_t offset;
     int ret;