diff --git a/include/nbytes.h b/include/nbytes.h
index 45ed4d4..525a917 100644
--- a/include/nbytes.h
+++ b/include/nbytes.h
@@ -4,6 +4,7 @@
 #include <cmath>
 #include <cstddef>
 #include <cstdint>
+#include <cstdlib>
 #include <cstring>
 #include <string>