diff --git a/include/input.h b/include/input.h
index 2f3ba3a..6d9cbd1 100644
--- a/include/input.h
+++ b/include/input.h
@@ -12,4 +12,4 @@ struct Input {
 };
 
 struct Input input_init(void);
-void input_update(struct Input *input);
+void input_update(struct Input *restrict input);
diff --git a/include/levelselection.h b/include/levelselection.h
index c739de8..77a63a0 100644
--- a/include/levelselection.h
+++ b/include/levelselection.h
@@ -23,6 +23,6 @@ struct LevelSelection {
 
 struct LevelSelection levelselection_init(void);
 /* Return 1 if game state should change. */
-int levelselection_update(struct LevelSelection *levelselection,
+int levelselection_update(struct LevelSelection *restrict levelselection,
                           struct Input input);
 void levelselection_draw(struct LevelSelection levelselection);
diff --git a/include/mainmenu.h b/include/mainmenu.h
index 1d68bbb..d177d69 100644
--- a/include/mainmenu.h
+++ b/include/mainmenu.h
@@ -18,5 +18,5 @@ struct MainMenu {
 
 struct MainMenu mainmenu_init(void);
 /* Return 1 if game state should change. */
-int mainmenu_update(struct MainMenu *mainmenu, struct Input input);
+int mainmenu_update(struct MainMenu *restrict mainmenu, struct Input input);
 void mainmenu_draw(struct MainMenu mainmenu);
diff --git a/include/pause.h b/include/pause.h
index 8e0fed3..0bbb666 100644
--- a/include/pause.h
+++ b/include/pause.h
@@ -10,5 +10,5 @@ struct Pause {
 
 struct Pause pause_init(void);
 /* Return 1 if game state should change. */
-int pause_update(struct Pause *pause, struct Input input);
+int pause_update(struct Pause *restrict pause, struct Input input);
 void pause_draw(struct Pause pause);
diff --git a/include/player.h b/include/player.h
index 9b032a5..4c16865 100644
--- a/include/player.h
+++ b/include/player.h
@@ -45,7 +45,7 @@ enum { UP_LEFT, UP_RIGHT, DOWN_LEFT, DOWN_RIGHT };
 struct Player player_init(void);
 void player_draw(struct Player player);
 /* return 1 if exit reached, -1 on death/reset and 0 otherwise */
-int player_update(struct Player *player, struct Input input);
+int player_update(struct Player *restrict player, struct Input input);
 void player_collide(Tile collisions[COLLIDE_POINTS], int x, int y, int margin);
 int player_collide_tile(Tile collisions[COLLIDE_POINTS], int x, int y,
                         Tile tile, int margin, int update);
diff --git a/include/titlescreen.h b/include/titlescreen.h
index 5532388..05b26ce 100644
--- a/include/titlescreen.h
+++ b/include/titlescreen.h
@@ -10,5 +10,6 @@ struct TitleScreen {
 
 struct TitleScreen titlescreen_init(void);
 /* Return 1 if game state should change. */
-int titlescreen_update(struct TitleScreen *titlescreen, struct Input input);
+int titlescreen_update(struct TitleScreen *restrict titlescreen,
+                       struct Input input);
 void titlescreen_draw(struct TitleScreen titlescreen);
diff --git a/include/transition.h b/include/transition.h
index 5bf0002..c47942d 100644
--- a/include/transition.h
+++ b/include/transition.h
@@ -21,7 +21,7 @@ struct Transition {
 
 struct Transition transition_init(float speed, color_t color,
                                   enum TransitionMode mode);
-enum TransitionMode transition_update(struct Transition *transition);
+enum TransitionMode transition_update(struct Transition *restrict transition);
 void transition_draw(struct Transition transition);
 void hfade_in(float step, color_t color);
 void hfade_out(float step, color_t color);
diff --git a/src/input/update.c b/src/input/update.c
index 98ae45b..4fa2823 100644
--- a/src/input/update.c
+++ b/src/input/update.c
@@ -5,7 +5,7 @@
 #include <gint/keyboard.h>
 
 void
-input_update(struct Input *input)
+input_update(struct Input *restrict input)
 {
 	int i;
 
diff --git a/src/levelselection/update.c b/src/levelselection/update.c
index b737d1f..c374b97 100644
--- a/src/levelselection/update.c
+++ b/src/levelselection/update.c
@@ -8,7 +8,8 @@
 
 /* Return 1 if game state should change. */
 int
-levelselection_update(struct LevelSelection *levelselection, struct Input input)
+levelselection_update(struct LevelSelection *restrict levelselection,
+                      struct Input input)
 {
 	/* decrease selected pack id */
 	if (input.keystates[K_LEFT] == KS_PRESS &&
diff --git a/src/mainmenu/update.c b/src/mainmenu/update.c
index 8ef7b00..1c7b930 100644
--- a/src/mainmenu/update.c
+++ b/src/mainmenu/update.c
@@ -7,7 +7,7 @@
 
 /* Return 1 if game state should change. */
 int
-mainmenu_update(struct MainMenu *mainmenu, struct Input input)
+mainmenu_update(struct MainMenu *restrict mainmenu, struct Input input)
 {
 	/* decrease selected pack id */
 	if (input.keystates[K_UP] == KS_PRESS ||
diff --git a/src/pause/update.c b/src/pause/update.c
index d24785e..03adf4b 100644
--- a/src/pause/update.c
+++ b/src/pause/update.c
@@ -6,7 +6,7 @@
 
 /* Return 1 if game state should change. */
 int
-pause_update(struct Pause *pause, struct Input input)
+pause_update(struct Pause *restrict pause, struct Input input)
 {
 	if (input.keystates[K_START] == KS_PRESS) {
 		return 1;
diff --git a/src/player/update.c b/src/player/update.c
index a07507a..6f48171 100644
--- a/src/player/update.c
+++ b/src/player/update.c
@@ -9,15 +9,16 @@
 #include "tiles.h"
 #include "util.h"
 
-static void player_move(struct Player *player, int x, int y);
-static void player_set_anim(struct Player *player, enum AnimState new_anim);
+static void player_move(struct Player *restrict player, int x, int y);
+static void player_set_anim(struct Player *restrict player,
+                            enum AnimState new_anim);
 
 extern struct Level level;
 
 /* return -1 on pause, return 1 if exit reached, 2 on death/reset and 0
  * otherwise */
 int
-player_update(struct Player *player, struct Input input)
+player_update(struct Player *restrict player, struct Input input)
 {
 	Tile collisions[COLLIDE_POINTS];
 	const int on_ground = player_collide_solid(player->x, player->y + 1);
@@ -194,7 +195,7 @@ player_update(struct Player *player, struct Input input)
 }
 
 static void
-player_move(struct Player *player, int x, int y)
+player_move(struct Player *restrict player, int x, int y)
 {
 	const int sign_x = sign(x);
 	const int sign_y = sign(y);
@@ -217,7 +218,7 @@ player_move(struct Player *player, int x, int y)
 }
 
 static void
-player_set_anim(struct Player *player, enum AnimState new_anim)
+player_set_anim(struct Player *restrict player, enum AnimState new_anim)
 {
 	player->anim_state = new_anim;
 	switch (new_anim) {
diff --git a/src/titlescreen/update.c b/src/titlescreen/update.c
index 2434adf..57bb204 100644
--- a/src/titlescreen/update.c
+++ b/src/titlescreen/update.c
@@ -6,7 +6,7 @@
 
 /* Return 1 if game state should change. */
 int
-titlescreen_update(struct TitleScreen *titlescreen, struct Input input)
+titlescreen_update(struct TitleScreen *restrict titlescreen, struct Input input)
 {
 	if (input.keystates[K_A] == KS_PRESS) {
 		return 1;
diff --git a/src/transition/update.c b/src/transition/update.c
index 62dfca2..ac5fc49 100644
--- a/src/transition/update.c
+++ b/src/transition/update.c
@@ -4,7 +4,7 @@
 #include "transition.h"
 
 enum TransitionMode
-transition_update(struct Transition *transition)
+transition_update(struct Transition *restrict transition)
 {
 	enum TransitionMode previous_transition_mode = TransitionNone;