diff --git a/src/core/ngx_string.h b/src/core/ngx_string.h
index 818a290..10f87ae 100644
--- a/src/core/ngx_string.h
+++ b/src/core/ngx_string.h
@@ -146,7 +146,8 @@
 void ngx_encode_base64(ngx_str_t *dst, ngx_str_t *src);
 ngx_int_t ngx_decode_base64(ngx_str_t *dst, ngx_str_t *src);
 
-size_t ngx_utf_length(ngx_str_t *utf);
+uint32_t ngx_utf_decode(u_char **p, size_t n);
+size_t ngx_utf_length(u_char *p, size_t n);
 u_char * ngx_utf_cpystrn(u_char *dst, u_char *src, size_t n);