diff --git a/src/core/include/mp-units/framework/symbol_text.h b/src/core/include/mp-units/framework/symbol_text.h
index faef17bb..af3a8452 100644
--- a/src/core/include/mp-units/framework/symbol_text.h
+++ b/src/core/include/mp-units/framework/symbol_text.h
@@ -63,7 +63,7 @@ constexpr bool is_basic_literal_character_set_char(char ch)
   return ch == 0x00 || (0x07 <= ch && ch <= 0x0D) || (0x20 <= ch && ch <= 0x7E);
 };
 
-template<std::size_t N, typename InputIt>
+template<typename InputIt>
 constexpr bool is_basic_literal_character_set(InputIt begin, InputIt end) noexcept
 {
   return all_of(begin, end, is_basic_literal_character_set_char);
@@ -78,7 +78,7 @@ constexpr bool is_basic_literal_character_set(const char (&txt)[N]) noexcept
 template<std::size_t N>
 constexpr fixed_u8string<N> to_u8string(fixed_string<N> txt)
 {
-  MP_UNITS_EXPECTS(is_basic_literal_character_set(txt));
+  MP_UNITS_EXPECTS(is_basic_literal_character_set(txt.begin(), txt.end()));
   return std::bit_cast<fixed_u8string<N>>(txt);
 }