diff --git a/cmdopt2/arg.hpp b/cmdopt2/arg.hpp
index 12a9508d..3098b30c 100644
--- a/cmdopt2/arg.hpp
+++ b/cmdopt2/arg.hpp
@@ -8,9 +8,10 @@
 
 #pragma once
 
+#include <cruft/util/cast.hpp>
+#include <cruft/util/concepts/string.hpp>
 #include <cruft/util/debug/assert.hpp>
 #include <cruft/util/parse/value.hpp>
-#include <cruft/util/cast.hpp>
 
 #include <optional>
 #include <string>
@@ -38,7 +39,7 @@ namespace cruft::cmdopt2 {
         bind (ValueT &ref)
         {
             CHECK (!acceptor1);
-            if constexpr (std::is_same_v<ValueT, std::string> or std::is_same_v<ValueT, char const*>) {
+            if constexpr (cruft::concepts::stringy<ValueT>) {
                 acceptor1 = [&ref] (std::string_view str) { ref = str; };
             } else {
                 acceptor1 = [&ref] (std::string_view str) { ref = parse::from_string<ValueT> (str); };