diff --git a/src/espcrc32builder.h b/src/espcrc32builder.h
index b4e9445..cc2ce4c 100644
--- a/src/espcrc32builder.h
+++ b/src/espcrc32builder.h
@@ -1,5 +1,8 @@
 #pragma once
 
+// system includes
+#include <cstddef>
+
 // esp-idf includes
 #include <esp32/rom/crc.h>