diff --git a/src/core/ngx_hash.h b/src/core/ngx_hash.h
index 95e0404..76e3c77 100644
--- a/src/core/ngx_hash.h
+++ b/src/core/ngx_hash.h
@@ -110,6 +110,8 @@
 #define ngx_hash(key, c)   ((ngx_uint_t) key * 31 + c)
 ngx_uint_t ngx_hash_key(u_char *data, size_t len);
 ngx_uint_t ngx_hash_key_lc(u_char *data, size_t len);
+ngx_uint_t ngx_hash_strlow(u_char *dst, u_char *src, size_t n);
+
 
 ngx_int_t ngx_hash_keys_array_init(ngx_hash_keys_arrays_t *ha, ngx_uint_t type);
 ngx_int_t ngx_hash_add_key(ngx_hash_keys_arrays_t *ha, ngx_str_t *key,