diff --git a/solanaceae/ngc_ft1_sha1/hash_utils.hpp b/solanaceae/ngc_ft1_sha1/hash_utils.hpp
index 4de52ec..d535aef 100644
--- a/solanaceae/ngc_ft1_sha1/hash_utils.hpp
+++ b/solanaceae/ngc_ft1_sha1/hash_utils.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cstdint>
+#include <cstddef>
 #include <vector>
 
 // returns the 20bytes sha1 hash