diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 41f504bc..aca308b3 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -96,7 +96,7 @@ not use GNU extensions.
 Brackets always go on the same line, including in functions.
 Always include brackets for if/while/for, even if it's a single statement.
 ```c
-void function() {
+void function(void) {
 	if (condition1) {
 		do_thing1();
 	}
diff --git a/examples/layer-shell.c b/examples/layer-shell.c
index ec25fe42..21ef3e93 100644
--- a/examples/layer-shell.c
+++ b/examples/layer-shell.c
@@ -149,7 +149,7 @@ static void draw(void) {
 	demo.last_frame = ts;
 }
 
-static void draw_popup() {
+static void draw_popup(void) {
 	static float alpha_mod = -0.01;
 
 	eglMakeCurrent(egl.display, popup_egl_surface, popup_egl_surface, egl.context);
@@ -188,7 +188,7 @@ static void xdg_popup_configure(void *data, struct xdg_popup *xdg_popup,
 	}
 }
 
-static void popup_destroy() {
+static void popup_destroy(void) {
 	wlr_egl_destroy_surface(&egl, popup_egl_surface);
 	wl_egl_window_destroy(popup_egl_window);
 	xdg_popup_destroy(popup);
diff --git a/examples/simple.c b/examples/simple.c
index 60acd7db..cbe60c98 100644
--- a/examples/simple.c
+++ b/examples/simple.c
@@ -143,7 +143,7 @@ void new_input_notify(struct wl_listener *listener, void *data) {
 	}
 }
 
-int main() {
+int main(void) {
 	wlr_log_init(L_DEBUG, NULL);
 	struct wl_display *display = wl_display_create();
 	struct sample_state state = {
diff --git a/render/gles2/renderer.c b/render/gles2/renderer.c
index e68bb83f..00a5c285 100644
--- a/render/gles2/renderer.c
+++ b/render/gles2/renderer.c
@@ -84,7 +84,7 @@ static void gles2_scissor(struct wlr_renderer *wlr_renderer,
 	POP_GLES2_DEBUG;
 }
 
-static void draw_quad() {
+static void draw_quad(void) {
 	GLfloat verts[] = {
 		1, 0, // top right
 		0, 0, // top left
diff --git a/types/wlr_cursor.c b/types/wlr_cursor.c
index 9a31fca2..32d990cf 100644
--- a/types/wlr_cursor.c
+++ b/types/wlr_cursor.c
@@ -56,7 +56,7 @@ struct wlr_cursor_state {
 	struct wl_listener layout_destroy;
 };
 
-struct wlr_cursor *wlr_cursor_create() {
+struct wlr_cursor *wlr_cursor_create(void) {
 	struct wlr_cursor *cur = calloc(1, sizeof(struct wlr_cursor));
 	if (!cur) {
 		wlr_log(L_ERROR, "Failed to allocate wlr_cursor");
diff --git a/types/wlr_output_layout.c b/types/wlr_output_layout.c
index 38329a48..bb1d399a 100644
--- a/types/wlr_output_layout.c
+++ b/types/wlr_output_layout.c
@@ -25,7 +25,7 @@ struct wlr_output_layout_output_state {
 	struct wl_listener output_destroy;
 };
 
-struct wlr_output_layout *wlr_output_layout_create() {
+struct wlr_output_layout *wlr_output_layout_create(void) {
 	struct wlr_output_layout *layout =
 		calloc(1, sizeof(struct wlr_output_layout));
 	if (layout == NULL) {
diff --git a/types/wlr_surface.c b/types/wlr_surface.c
index 3949f3e2..61284416 100644
--- a/types/wlr_surface.c
+++ b/types/wlr_surface.c
@@ -570,7 +570,7 @@ struct wlr_surface *wlr_surface_from_resource(struct wl_resource *resource) {
 	return wl_resource_get_user_data(resource);
 }
 
-static struct wlr_surface_state *surface_state_create() {
+static struct wlr_surface_state *surface_state_create(void) {
 	struct wlr_surface_state *state =
 		calloc(1, sizeof(struct wlr_surface_state));
 	if (state == NULL) {