diff --git a/src/crypto/CryptoNight_constants.h b/src/crypto/CryptoNight_constants.h
index 3feb5697..f7a9542b 100644
--- a/src/crypto/CryptoNight_constants.h
+++ b/src/crypto/CryptoNight_constants.h
@@ -27,6 +27,7 @@
 #define XMRIG_CRYPTONIGHT_CONSTANTS_H
 
 
+#include <stddef.h>
 #include <stdint.h>