diff --git a/include/tic80.h b/include/tic80.h
index 325b5b63c..991d22a94 100644
--- a/include/tic80.h
+++ b/include/tic80.h
@@ -186,7 +186,7 @@ typedef struct
 
 TIC80_API tic80* tic80_create(s32 samplerate, tic80_pixel_color_format format);
 TIC80_API void tic80_load(tic80* tic, void* cart, s32 size);
-TIC80_API void tic80_tick(tic80* tic, tic80_input input, u64 (*counter)(), u64 (*freq)());
+TIC80_API void tic80_tick(tic80* tic, tic80_input input, u64 (*counter)(void*), u64 (*freq)(void*));
 TIC80_API void tic80_sound(tic80* tic);
 TIC80_API void tic80_delete(tic80* tic);
 
diff --git a/src/system/libretro/tic80_libretro.c b/src/system/libretro/tic80_libretro.c
index 322d365bb..dc5435c3a 100644
--- a/src/system/libretro/tic80_libretro.c
+++ b/src/system/libretro/tic80_libretro.c
@@ -84,7 +84,7 @@ static struct tic80_state* state = NULL;
 /**
  * TIC-80 callback; Request counter.
  */
-static u64 tic80_libretro_counter()
+static u64 tic80_libretro_counter(void* data)
 {
 	if (state == NULL) {
 		return 0;
@@ -96,7 +96,7 @@ static u64 tic80_libretro_counter()
 /**
  * TIC-80 callback; Request frequency.
  */
-static u64 tic80_libretro_frequency()
+static u64 tic80_libretro_frequency(void* data)
 {
 	return TIC80_FREQUENCY;
 }
diff --git a/src/system/sdl/player.c b/src/system/sdl/player.c
index d9d765532..dc36e1819 100644
--- a/src/system/sdl/player.c
+++ b/src/system/sdl/player.c
@@ -48,12 +48,12 @@ static void onExit()
     state.quit = true;
 }
 
-static u64 tic_sys_counter_get()
+static u64 tic_sys_counter_get(void* data)
 {
     return SDL_GetPerformanceCounter();
 }
 
-static u64 tic_sys_freq_get()
+static u64 tic_sys_freq_get(void* data)
 {
     return SDL_GetPerformanceFrequency();
 }