diff --git a/AK/Types.h b/AK/Types.h
index a93303ffaa..5575be3e09 100644
--- a/AK/Types.h
+++ b/AK/Types.h
@@ -63,6 +63,7 @@ typedef int pid_t;
 
 #else
 #    include <stdint.h>
+#    include <stddef.h>
 #    include <sys/types.h>
 
 #    ifdef __ptrdiff_t