diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index 64ba703..2da6c83 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -952,7 +952,7 @@
 
 
 /*
- * ngx_utf_decode() decodes two and more bytes UTF sequences only
+ * ngx_utf8_decode() decodes two and more bytes UTF sequences only
  * the return values:
  *    0x80 - 0x10ffff         valid character
  *    0x110000 - 0xfffffffd   invalid sequence
@@ -961,7 +961,7 @@
  */
 
 uint32_t
-ngx_utf_decode(u_char **p, size_t n)
+ngx_utf8_decode(u_char **p, size_t n)
 {
     size_t    len;
     uint32_t  u, i, valid;
@@ -1018,7 +1018,7 @@
 
 
 size_t
-ngx_utf_length(u_char *p, size_t n)
+ngx_utf8_length(u_char *p, size_t n)
 {
     u_char  c, *last;
     size_t  len;
@@ -1034,8 +1034,8 @@
             continue;
         }
 
-        if (ngx_utf_decode(&p, n) > 0x10ffff) {
-            /* invalid utf */
+        if (ngx_utf8_decode(&p, n) > 0x10ffff) {
+            /* invalid UTF-8 */
             return n;
         }
     }
@@ -1045,7 +1045,7 @@
 
 
 u_char *
-ngx_utf_cpystrn(u_char *dst, u_char *src, size_t n, size_t len)
+ngx_utf8_cpystrn(u_char *dst, u_char *src, size_t n, size_t len)
 {
     u_char  c, *next;
 
@@ -1073,8 +1073,8 @@
 
         next = src;
 
-        if (ngx_utf_decode(&next, len) > 0x10ffff) {
-            /* invalid utf */
+        if (ngx_utf8_decode(&next, len) > 0x10ffff) {
+            /* invalid UTF-8 */
             break;
         }
 
diff --git a/src/core/ngx_string.h b/src/core/ngx_string.h
index 895925b..dfb3bc4 100644
--- a/src/core/ngx_string.h
+++ b/src/core/ngx_string.h
@@ -151,9 +151,9 @@
 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);
 
-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, size_t len);
+uint32_t ngx_utf8_decode(u_char **p, size_t n);
+size_t ngx_utf8_length(u_char *p, size_t n);
+u_char *ngx_utf8_cpystrn(u_char *dst, u_char *src, size_t n, size_t len);
 
 
 #define NGX_ESCAPE_URI         0
diff --git a/src/http/modules/ngx_http_autoindex_module.c b/src/http/modules/ngx_http_autoindex_module.c
index 64b29a8..86b7c0b 100644
--- a/src/http/modules/ngx_http_autoindex_module.c
+++ b/src/http/modules/ngx_http_autoindex_module.c
@@ -329,7 +329,7 @@
                                            NGX_ESCAPE_HTML);
 
         if (r->utf8) {
-            entry->utf_len = ngx_utf_length(entry->name.data, entry->name.len);
+            entry->utf_len = ngx_utf8_length(entry->name.data, entry->name.len);
         } else {
             entry->utf_len = len;
         }
@@ -420,8 +420,8 @@
                 utf_len = NGX_HTTP_AUTOINDEX_NAME_LEN + 1;
             }
 
-            b->last = ngx_utf_cpystrn(b->last, entry[i].name.data,
-                                      utf_len, entry[i].name.len + 1);
+            b->last = ngx_utf8_cpystrn(b->last, entry[i].name.data,
+                                       utf_len, entry[i].name.len + 1);
             last = b->last;
 
         } else {
diff --git a/src/http/modules/ngx_http_charset_filter_module.c b/src/http/modules/ngx_http_charset_filter_module.c
index a5db2d8..8ca859b 100644
--- a/src/http/modules/ngx_http_charset_filter_module.c
+++ b/src/http/modules/ngx_http_charset_filter_module.c
@@ -642,7 +642,7 @@
                 size = buf->last - src;
 
                 saved = src;
-                n = ngx_utf_decode(&saved, size);
+                n = ngx_utf8_decode(&saved, size);
 
                 if (n == 0xfffffffe) {
                     /* incomplete UTF-8 symbol */
@@ -710,7 +710,7 @@
     }
 
     saved = ctx->saved;
-    n = ngx_utf_decode(&saved, i);
+    n = ngx_utf8_decode(&saved, i);
 
     c = '\0';
 
@@ -818,7 +818,7 @@
 
         len = buf->last - src;
 
-        n = ngx_utf_decode(&src, len);
+        n = ngx_utf8_decode(&src, len);
 
         if (n < 0x10000) {
 
@@ -1270,7 +1270,7 @@
 
         p = &table->src2dst[src * NGX_UTF_LEN] + 1;
 
-        n = ngx_utf_decode(&p, i);
+        n = ngx_utf8_decode(&p, i);
 
         if (n > 0xffff) {
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,