diff --git a/ext/imap/php_imap.c b/ext/imap/php_imap.c
index 86eb2d9a5f9..43527d276ee 100644
--- a/ext/imap/php_imap.c
+++ b/ext/imap/php_imap.c
@@ -1993,8 +1993,8 @@ PHP_FUNCTION(imap_rfc822_parse_adrlist)
 }
 /* }}} */
 
-/* {{{ proto string imap_utf8(string string)
-   Convert a string to UTF-8 */
+/* {{{ proto string imap_utf8(string mime_encoded_text)
+   Convert a mime-encoded text to UTF-8 */
 PHP_FUNCTION(imap_utf8)
 {
 	zval **str;