diff --git a/src/include/xfor/exttype.h b/src/include/xfor/exttype.h
index f612c5c..9f94784 100644
--- a/src/include/xfor/exttype.h
+++ b/src/include/xfor/exttype.h
@@ -99,7 +99,7 @@ namespace MultiArrayHelper
 
     struct None
     {
-        static constexpr size_t VAL = 0;
+        size_t VAL = 0;
         None() = default;
         None(const None& in) = default;
         None(None&& in) = default;