diff --git a/lib/evmone/errors.hpp b/lib/evmone/errors.hpp
index fc6ed70c4b..76ea7815b5 100644
--- a/lib/evmone/errors.hpp
+++ b/lib/evmone/errors.hpp
@@ -29,9 +29,9 @@ inline const std::error_category& evmone_category() noexcept
 {
     struct evmone_category_impl : std::error_category
     {
-        const char* name() const noexcept final { return "evmone"; }
+        [[nodiscard]] const char* name() const noexcept final { return "evmone"; }
 
-        std::string message(int ev) const noexcept final
+        [[nodiscard]] std::string message(int ev) const noexcept final
         {
             switch (ev)
             {
@@ -72,7 +72,7 @@ inline const std::error_category& evmone_category() noexcept
 /// This is used by std::error_code to implement implicit conversion
 /// evmone::ErrorCode -> std::error_code, therefore the definition is
 /// in the global namespace to match the definition of ethash_errc.
-std::error_code make_error_code(ErrorCode errc) noexcept
+inline std::error_code make_error_code(ErrorCode errc) noexcept
 {
     return {errc, evmone_category()};
 }