diff --git a/include/beman/cstring_view/cstring_view.hpp b/include/beman/cstring_view/cstring_view.hpp
index a698e6b..dda8a66 100644
--- a/include/beman/cstring_view/cstring_view.hpp
+++ b/include/beman/cstring_view/cstring_view.hpp
@@ -168,7 +168,7 @@ class basic_cstring_view {
     constexpr const_pointer data() const noexcept { return data_; }
     constexpr const_pointer c_str() const noexcept { return data_; }
 
-    operator std::basic_string_view<charT, traits>() const noexcept {
+    constexpr operator std::basic_string_view<charT, traits>() const noexcept {
         return std::basic_string_view<charT, traits>{data_, size_};
     }