diff --git a/app/src/command.c b/app/src/command.c
index cc11a0de..e6e63ca7 100644
--- a/app/src/command.c
+++ b/app/src/command.c
@@ -9,7 +9,7 @@
 
 static const char *adb_command;
 
-static inline const char *get_adb_command() {
+static inline const char *get_adb_command(void) {
     if (!adb_command) {
         adb_command = getenv("ADB");
         if (!adb_command)
diff --git a/app/tests/test_control_event_queue.c b/app/tests/test_control_event_queue.c
index 07e547c1..a27181b6 100644
--- a/app/tests/test_control_event_queue.c
+++ b/app/tests/test_control_event_queue.c
@@ -3,7 +3,7 @@
 
 #include "control_event.h"
 
-static void test_control_event_queue_empty() {
+static void test_control_event_queue_empty(void) {
     struct control_event_queue queue;
     SDL_bool init_ok = control_event_queue_init(&queue);
     assert(init_ok);
@@ -25,7 +25,7 @@ static void test_control_event_queue_empty() {
     control_event_queue_destroy(&queue);
 }
 
-static void test_control_event_queue_full() {
+static void test_control_event_queue_full(void) {
     struct control_event_queue queue;
     SDL_bool init_ok = control_event_queue_init(&queue);
     assert(init_ok);
@@ -43,7 +43,7 @@ static void test_control_event_queue_full() {
     control_event_queue_destroy(&queue);
 }
 
-static void test_control_event_queue_push_take() {
+static void test_control_event_queue_push_take(void) {
     struct control_event_queue queue;
     SDL_bool init_ok = control_event_queue_init(&queue);
     assert(init_ok);
@@ -87,7 +87,7 @@ static void test_control_event_queue_push_take() {
     control_event_queue_destroy(&queue);
 }
 
-int main() {
+int main(void) {
     test_control_event_queue_empty();
     test_control_event_queue_full();
     test_control_event_queue_push_take();
diff --git a/app/tests/test_control_event_serialize.c b/app/tests/test_control_event_serialize.c
index ad472776..21d7909b 100644
--- a/app/tests/test_control_event_serialize.c
+++ b/app/tests/test_control_event_serialize.c
@@ -3,7 +3,7 @@
 
 #include "control_event.h"
 
-static void test_serialize_keycode_event() {
+static void test_serialize_keycode_event(void) {
     struct control_event event = {
         .type = CONTROL_EVENT_TYPE_KEYCODE,
         .keycode_event = {
@@ -26,7 +26,7 @@ static void test_serialize_keycode_event() {
     assert(!memcmp(buf, expected, sizeof(expected)));
 }
 
-static void test_serialize_text_event() {
+static void test_serialize_text_event(void) {
     struct control_event event = {
         .type = CONTROL_EVENT_TYPE_TEXT,
         .text_event = {
@@ -46,7 +46,7 @@ static void test_serialize_text_event() {
     assert(!memcmp(buf, expected, sizeof(expected)));
 }
 
-static void test_serialize_long_text_event() {
+static void test_serialize_long_text_event(void) {
     struct control_event event;
     event.type = CONTROL_EVENT_TYPE_TEXT;
     char text[TEXT_MAX_LENGTH];
@@ -66,7 +66,7 @@ static void test_serialize_long_text_event() {
     assert(!memcmp(buf, expected, sizeof(expected)));
 }
 
-static void test_serialize_mouse_event() {
+static void test_serialize_mouse_event(void) {
     struct control_event event = {
         .type = CONTROL_EVENT_TYPE_MOUSE,
         .mouse_event = {
@@ -99,7 +99,7 @@ static void test_serialize_mouse_event() {
     assert(!memcmp(buf, expected, sizeof(expected)));
 }
 
-static void test_serialize_scroll_event() {
+static void test_serialize_scroll_event(void) {
     struct control_event event = {
         .type = CONTROL_EVENT_TYPE_SCROLL,
         .scroll_event = {
@@ -132,11 +132,10 @@ static void test_serialize_scroll_event() {
     assert(!memcmp(buf, expected, sizeof(expected)));
 }
 
-int main() {
+int main(void) {
     test_serialize_keycode_event();
     test_serialize_text_event();
     test_serialize_long_text_event();
     test_serialize_mouse_event();
     test_serialize_scroll_event();
-    return 0;
 }
diff --git a/app/tests/test_strutil.c b/app/tests/test_strutil.c
index b00e01fe..1dd7fbbe 100644
--- a/app/tests/test_strutil.c
+++ b/app/tests/test_strutil.c
@@ -3,7 +3,7 @@
 
 #include "str_util.h"
 
-static void test_xstrncpy_simple() {
+static void test_xstrncpy_simple(void) {
     char s[] = "xxxxxxxxxx";
     size_t w = xstrncpy(s, "abcdef", sizeof(s));
 
@@ -20,7 +20,7 @@ static void test_xstrncpy_simple() {
     assert(!strcmp("abcdef", s));
 }
 
-static void test_xstrncpy_just_fit() {
+static void test_xstrncpy_just_fit(void) {
     char s[] = "xxxxxx";
     size_t w = xstrncpy(s, "abcdef", sizeof(s));
 
@@ -34,7 +34,7 @@ static void test_xstrncpy_just_fit() {
     assert(!strcmp("abcdef", s));
 }
 
-static void test_xstrncpy_truncated() {
+static void test_xstrncpy_truncated(void) {
     char s[] = "xxx";
     size_t w = xstrncpy(s, "abcdef", sizeof(s));
 
@@ -48,7 +48,7 @@ static void test_xstrncpy_truncated() {
     assert(!strncmp("abcdef", s, 3));
 }
 
-static void test_xstrjoin_simple() {
+static void test_xstrjoin_simple(void) {
     const char *const tokens[] = { "abc", "de", "fghi", NULL };
     char s[] = "xxxxxxxxxxxxxx";
     size_t w = xstrjoin(s, tokens, ' ', sizeof(s));
@@ -66,7 +66,7 @@ static void test_xstrjoin_simple() {
     assert(!strcmp("abc de fghi", s));
 }
 
-static void test_xstrjoin_just_fit() {
+static void test_xstrjoin_just_fit(void) {
     const char *const tokens[] = { "abc", "de", "fghi", NULL };
     char s[] = "xxxxxxxxxxx";
     size_t w = xstrjoin(s, tokens, ' ', sizeof(s));
@@ -81,7 +81,7 @@ static void test_xstrjoin_just_fit() {
     assert(!strcmp("abc de fghi", s));
 }
 
-static void test_xstrjoin_truncated_in_token() {
+static void test_xstrjoin_truncated_in_token(void) {
     const char *const tokens[] = { "abc", "de", "fghi", NULL };
     char s[] = "xxxxx";
     size_t w = xstrjoin(s, tokens, ' ', sizeof(s));
@@ -96,7 +96,7 @@ static void test_xstrjoin_truncated_in_token() {
     assert(!strcmp("abc d", s));
 }
 
-static void test_xstrjoin_truncated_before_sep() {
+static void test_xstrjoin_truncated_before_sep(void) {
     const char *const tokens[] = { "abc", "de", "fghi", NULL };
     char s[] = "xxxxxx";
     size_t w = xstrjoin(s, tokens, ' ', sizeof(s));
@@ -111,7 +111,7 @@ static void test_xstrjoin_truncated_before_sep() {
     assert(!strcmp("abc de", s));
 }
 
-static void test_xstrjoin_truncated_after_sep() {
+static void test_xstrjoin_truncated_after_sep(void) {
     const char *const tokens[] = { "abc", "de", "fghi", NULL };
     char s[] = "xxxxxxx";
     size_t w = xstrjoin(s, tokens, ' ', sizeof(s));
@@ -126,7 +126,7 @@ static void test_xstrjoin_truncated_after_sep() {
     assert(!strcmp("abc de ", s));
 }
 
-int main() {
+int main(void) {
     test_xstrncpy_simple();
     test_xstrncpy_just_fit();
     test_xstrncpy_truncated();