diff --git a/src/blackmisc/index_sequence.h b/src/blackmisc/index_sequence.h
index 5ed4d932d..0d522c72f 100644
--- a/src/blackmisc/index_sequence.h
+++ b/src/blackmisc/index_sequence.h
@@ -8,6 +8,7 @@
 
 #include <tuple>
 #include <type_traits>
+#include <cstddef>
 
 namespace BlackMisc
 {