diff --git a/src/native/skate3_native_diag.h b/src/native/skate3_native_diag.h
index 94f2562..6600a84 100644
--- a/src/native/skate3_native_diag.h
+++ b/src/native/skate3_native_diag.h
@@ -9,6 +9,7 @@
 // TU.
 
 #include <atomic>
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <mutex>
diff --git a/src/skate3_native_scene.h b/src/skate3_native_scene.h
index 9c198ff..693d9f1 100644
--- a/src/skate3_native_scene.h
+++ b/src/skate3_native_scene.h
@@ -7,6 +7,7 @@
 // guest output texture via the SDK native-guest-output hook, replacing the
 // emulated frame when active.
 
+#include <cstddef>
 #include <cstdint>
 #include <vector>
 
diff --git a/src/skate3_native_scene_state.h b/src/skate3_native_scene_state.h
index 93562c8..b821257 100644
--- a/src/skate3_native_scene_state.h
+++ b/src/skate3_native_scene_state.h
@@ -9,6 +9,7 @@
 #include <array>
 #include <atomic>
 #include <chrono>
+#include <cstddef>
 #include <condition_variable>
 #include <cstdint>
 #include <cstdio>
diff --git a/src/skate3_ultrawide_guest.h b/src/skate3_ultrawide_guest.h
index d25dce4..859ff50 100644
--- a/src/skate3_ultrawide_guest.h
+++ b/src/skate3_ultrawide_guest.h
@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <array>
 #include <cmath>
+#include <cstddef>
 #include <cstdint>
 
 #include <rex/cvar.h>