diff --git a/src/wayland-util.h b/src/wayland-util.h
index 642a04bc..1b8fd4b4 100644
--- a/src/wayland-util.h
+++ b/src/wayland-util.h
@@ -27,6 +27,7 @@
 extern "C" {
 #endif
 
+#include <stddef.h>
 #include <inttypes.h>
 
 /* GCC visibility */