diff --git a/include/fmt/base.h b/include/fmt/base.h
index 61115d9f..b5d1c52e 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -2660,8 +2660,9 @@ template <typename... T> struct fstring {
   template <typename S,
             FMT_ENABLE_IF(std::is_convertible<const S&, string_view>::value)>
   FMT_CONSTEVAL FMT_ALWAYS_INLINE fstring(const S& s) : str(s) {
+    FMT_CONSTEXPR auto sv = string_view(S());
     if (FMT_USE_CONSTEVAL)
-      detail::parse_format_string<char>(s, checker(s, arg_pack()));
+      detail::parse_format_string<char>(sv, checker(sv, arg_pack()));
 #ifdef FMT_ENFORCE_COMPILE_STRING
     static_assert(
         FMT_USE_CONSTEVAL && sizeof(s) != 0,