diff --git a/Sources/kinc/audio2/audio.h b/Sources/kinc/audio2/audio.h
index 79e11df36..c5492b5d8 100644
--- a/Sources/kinc/audio2/audio.h
+++ b/Sources/kinc/audio2/audio.h
@@ -70,6 +70,7 @@ void kinc_a2_internal_sample_rate_callback(void);
 
 #include <kinc/threads/mutex.h>
 #include <memory.h>
+#include <stddef.h>
 
 static kinc_mutex_t mutex;
 
diff --git a/Sources/kinc/graphics4/pipeline.c.h b/Sources/kinc/graphics4/pipeline.c.h
index 13e630469..35b308ae1 100644
--- a/Sources/kinc/graphics4/pipeline.c.h
+++ b/Sources/kinc/graphics4/pipeline.c.h
@@ -1,5 +1,7 @@
 #include "pipeline.h"
 
+#include <stddef.h>
+
 void kinc_g4_internal_pipeline_set_defaults(kinc_g4_pipeline_t *state) {
 	for (int i = 0; i < 16; ++i)
 		state->input_layout[i] = NULL;
diff --git a/Sources/kinc/input/acceleration.h b/Sources/kinc/input/acceleration.h
index 390545d31..d924d87d1 100644
--- a/Sources/kinc/input/acceleration.h
+++ b/Sources/kinc/input/acceleration.h
@@ -25,6 +25,7 @@ void kinc_internal_on_acceleration(float x, float y, float z);
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 void (*acceleration_callback)(float /*x*/, float /*y*/, float /*z*/) = NULL;
 
diff --git a/Sources/kinc/input/gamepad.h b/Sources/kinc/input/gamepad.h
index d4cb00881..a2776bd3e 100644
--- a/Sources/kinc/input/gamepad.h
+++ b/Sources/kinc/input/gamepad.h
@@ -63,6 +63,7 @@ void kinc_internal_gamepad_trigger_button(int gamepad, int button, float value);
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*gamepad_axis_callback)(int /*gamepad*/, int /*axis*/, float /*value*/, void * /*userdata*/) = NULL;
 static void *gamepad_axis_callback_userdata = NULL;
diff --git a/Sources/kinc/input/keyboard.h b/Sources/kinc/input/keyboard.h
index 031539028..788f845c6 100644
--- a/Sources/kinc/input/keyboard.h
+++ b/Sources/kinc/input/keyboard.h
@@ -245,6 +245,7 @@ void kinc_internal_keyboard_trigger_key_press(unsigned character);
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*keyboard_key_down_callback)(int /*key_code*/, void * /*data*/) = NULL;
 static void *keyboard_key_down_callback_data = NULL;
diff --git a/Sources/kinc/input/mouse.h b/Sources/kinc/input/mouse.h
index 3d76dd04f..3fec1813e 100644
--- a/Sources/kinc/input/mouse.h
+++ b/Sources/kinc/input/mouse.h
@@ -140,6 +140,7 @@ void kinc_internal_mouse_window_deactivated(int window);
 #define KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*mouse_press_callback)(int /*window*/, int /*button*/, int /*x*/, int /*y*/, void * /*data*/) = NULL;
 static void *mouse_press_callback_data = NULL;
diff --git a/Sources/kinc/input/pen.h b/Sources/kinc/input/pen.h
index d16e957ed..a20e1e271 100644
--- a/Sources/kinc/input/pen.h
+++ b/Sources/kinc/input/pen.h
@@ -61,6 +61,7 @@ void kinc_internal_eraser_trigger_release(int window, int x, int y, float pressu
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*pen_press_callback)(int /*window*/, int /*x*/, int /*y*/, float /*pressure*/) = NULL;
 static void (*pen_move_callback)(int /*window*/, int /*x*/, int /*y*/, float /*pressure*/) = NULL;
diff --git a/Sources/kinc/input/rotation.h b/Sources/kinc/input/rotation.h
index 3bf2dd131..7a715be7f 100644
--- a/Sources/kinc/input/rotation.h
+++ b/Sources/kinc/input/rotation.h
@@ -25,6 +25,7 @@ void kinc_internal_on_rotation(float x, float y, float z);
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*rotation_callback)(float /*x*/, float /*y*/, float /*z*/) = NULL;
 
diff --git a/Sources/kinc/input/surface.h b/Sources/kinc/input/surface.h
index f61d8dfec..d08c50b26 100644
--- a/Sources/kinc/input/surface.h
+++ b/Sources/kinc/input/surface.h
@@ -39,6 +39,7 @@ void kinc_internal_surface_trigger_touch_end(int index, int x, int y);
 #ifdef KINC_IMPLEMENTATION
 
 #include <memory.h>
+#include <stddef.h>
 
 static void (*surface_touch_start_callback)(int /*index*/, int /*x*/, int /*y*/) = NULL;
 static void (*surface_move_callback)(int /*index*/, int /*x*/, int /*y*/) = NULL;