diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index 9d653ed886..bad3150d92 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -5,10 +5,11 @@ Track Selection
 ---------------
 
 ``--alang=<languagecode[,languagecode,...]>``
-    Specify a priority list of audio languages to use. Different container
-    formats employ different language codes. DVDs use ISO 639-1 two-letter
-    language codes, Matroska, MPEG-TS and NUT use ISO 639-2 three-letter
-    language codes, while OGM uses a free-form identifier. See also ``--aid``.
+    Specify a priority list of audio languages to use, as IETF language tags.
+    Equivalent ISO 639-1 two-letter and ISO 639-2 three-letter codes are treated the same.
+    The first tag in the list whose language matches a track in the file will be used.
+    A track that matches more subtags will be preferred over one that matches fewer,
+    with preference given to earlier subtags over later ones. See also ``--aid``.
 
     This is a string list option. See `List Options`_ for details.
 
@@ -20,10 +21,7 @@ Track Selection
           audio.
 
 ``--slang=<languagecode[,languagecode,...]>``
-    Specify a priority list of subtitle languages to use. Different container
-    formats employ different language codes. DVDs use ISO 639-1 two letter
-    language codes, Matroska uses ISO 639-2 three letter language codes while
-    OGM uses a free-form identifier. See also ``--sid``.
+    Equivalent to ``--alang``, for subtitle tracks.
 
     This is a string list option. See `List Options`_ for details.
 
@@ -33,6 +31,8 @@ Track Selection
           a DVD and falls back on English if Hungarian is not available.
         - ``mpv --slang=jpn example.mkv`` plays a Matroska file with Japanese
           subtitles.
+        - ``mpv --slang=pt-BR example.mkv`` plays a Matroska file with Brazilian
+          Portuguese subtitles if available, and otherwise any Portuguese subtitles.
 
 ``--vlang=<...>``
     Equivalent to ``--alang`` and ``--slang``, for video tracks.
diff --git a/player/loadfile.c b/player/loadfile.c
index 009d1471ad..5095f6a49f 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -47,6 +47,7 @@
 #include "common/recorder.h"
 #include "common/stats.h"
 #include "input/input.h"
+#include "misc/language.h"
 
 #include "audio/out/ao.h"
 #include "filters/f_decoder_wrapper.h"
@@ -447,8 +448,9 @@ static int match_lang(char **langs, const char *lang)
     if (!lang)
         return 0;
     for (int idx = 0; langs && langs[idx]; idx++) {
-        if (lang && strcasecmp(langs[idx], lang) == 0)
-            return INT_MAX - idx;
+        int score = mp_match_lang_single(langs[idx], lang);
+        if (score > 0)
+            return INT_MAX - (idx + 1) * LANGUAGE_SCORE_MAX + score - 1;
     }
     return 0;
 }