--- a/lib/xray/xray_buffer_queue.h
+++ b/lib/xray/xray_buffer_queue.h
@@ -17,6 +17,7 @@
 
 #include "sanitizer_common/sanitizer_atomic.h"
 #include "sanitizer_common/sanitizer_mutex.h"
+#include <cstddef>
 #include <deque>
 #include <unordered_set>
 #include <utility>