diff --git a/eek/eek-renderer.c b/eek/eek-renderer.c
index ceeeb02d..8e62c560 100644
--- a/eek/eek-renderer.c
+++ b/eek/eek-renderer.c
@@ -241,7 +241,7 @@ static GType new_type(char *name) {
     );
 }
 
-static GType view_type() {
+static GType view_type(void) {
     static GType type = 0;
     if (!type) {
         type = new_type("sq_view");
@@ -249,7 +249,7 @@ static GType view_type() {
     return type;
 }
 
-static GType button_type() {
+static GType button_type(void) {
     static GType type = 0;
     if (!type) {
         type = new_type("sq_button");
diff --git a/src/outputs.h b/src/outputs.h
index e018d037..f6466a70 100644
--- a/src/outputs.h
+++ b/src/outputs.h
@@ -9,7 +9,7 @@ struct squeek_output_handle {
     struct squeek_outputs *outputs;
 };
 
-struct squeek_outputs *squeek_outputs_new();
+struct squeek_outputs *squeek_outputs_new(void);
 void squeek_outputs_free(struct squeek_outputs*);
 void squeek_outputs_register(struct squeek_outputs*, struct wl_output *output);
 struct squeek_output_handle squeek_outputs_get_current(struct squeek_outputs*);
diff --git a/src/style.h b/src/style.h
index 6fd7c8b7..fdc7d463 100644
--- a/src/style.h
+++ b/src/style.h
@@ -2,6 +2,6 @@
 #define __STYLE_H
 #include "gtk/gtk.h"
 
-GtkCssProvider *squeek_load_style();
+GtkCssProvider *squeek_load_style(void);
 
 #endif
diff --git a/src/ui_manager.h b/src/ui_manager.h
index 57d3cc70..b0c64592 100644
--- a/src/ui_manager.h
+++ b/src/ui_manager.h
@@ -7,7 +7,7 @@
 
 struct ui_manager;
 
-struct ui_manager *squeek_uiman_new();
+struct ui_manager *squeek_uiman_new(void);
 void squeek_uiman_set_output(struct ui_manager *uiman, struct squeek_output_handle output);
 uint32_t squeek_uiman_get_perceptual_height(struct ui_manager *uiman);