diff --git a/source/utf8/cpp17.h b/source/utf8/cpp17.h
index 34d94c0..7bfa869 100644
--- a/source/utf8/cpp17.h
+++ b/source/utf8/cpp17.h
@@ -29,12 +29,16 @@ DEALINGS IN THE SOFTWARE.
 #define UTF8_FOR_CPP_7e906c01_03a3_4daf_b420_ea7ea952b3c9
 
 #include "checked.h"
-#include "cpp11.h"
 #include <string>
 
 namespace utf8
 {
 
+    inline void append(char32_t cp, std::string& s)
+    {
+        append(uint32_t(cp), std::back_inserter(s));
+    }
+
     inline std::string utf16to8(std::u16string_view s)
     {
         std::string result;