diff --git a/include/xo/object2/DFloat.hpp b/include/xo/object2/DFloat.hpp
index 0812a59..ab38d07 100644
--- a/include/xo/object2/DFloat.hpp
+++ b/include/xo/object2/DFloat.hpp
@@ -14,6 +14,7 @@ namespace xo {
         struct DFloat {
             using AAllocator = xo::mm::AAllocator;
             using ppindentinfo = xo::print::ppindentinfo;
+            using value_type = double;
 
             explicit DFloat(double x) : value_{x} {}
 
diff --git a/include/xo/object2/DInteger.hpp b/include/xo/object2/DInteger.hpp
index d125fc4..8cb109f 100644
--- a/include/xo/object2/DInteger.hpp
+++ b/include/xo/object2/DInteger.hpp
@@ -15,6 +15,7 @@ namespace xo {
         struct DInteger {
             using AAllocator = xo::mm::AAllocator;
             using ppindentinfo = xo::print::ppindentinfo;
+            using value_type = long;
 
             explicit DInteger(long x) : value_{x} {}