diff --git a/misc/language.c b/misc/language.c
index 0d9d0689da..028437f1b6 100644
--- a/misc/language.c
+++ b/misc/language.c
@@ -21,7 +21,7 @@
 #include <stdint.h>
 
 #include "common/common.h"
-#include "misc/bstr.h"
+#include "misc/ctype.h"
 
 #define L(s) { #s, sizeof(#s) - 1 }
 
@@ -296,3 +296,56 @@ done:
     talloc_free(ta_ctx);
     return best_score;
 }
+
+bstr mp_guess_lang_from_filename(bstr name, int *lang_start)
+{
+    name = bstr_strip(bstr_strip_ext(name));
+
+    if (name.len < 2)
+        return (bstr){0};
+
+    int lang_length = 0;
+    int i = name.len - 1;
+    int suffixes_length = 0;
+
+    char delimiter = '.';
+    if (name.start[i] == ')') {
+        delimiter = '(';
+        i--;
+    }
+    if (name.start[i] == ']') {
+        delimiter = '[';
+        i--;
+    }
+
+    while (true) {
+        while (i >= 0 && mp_isalpha(name.start[i])) {
+            lang_length++;
+            i--;
+        }
+
+        // According to
+        // https://en.wikipedia.org/wiki/IETF_language_tag#Syntax_of_language_tags
+        // subtags after the first are composed of 1 to 8 letters.
+        if (lang_length < suffixes_length + 1 || lang_length > suffixes_length + 8)
+            return (bstr){0};
+
+        if (i >= 0 && name.start[i] == '-') {
+            lang_length++;
+            i--;
+            suffixes_length = lang_length;
+        } else {
+            break;
+        }
+    }
+
+    // The primary subtag can have 2 or 3 letters.
+    if (lang_length < suffixes_length + 2 || lang_length > suffixes_length + 3 ||
+        i <= 0 || name.start[i] != delimiter)
+        return (bstr){0};
+
+    if (lang_start)
+        *lang_start = i;
+
+    return (bstr){name.start + i + 1, lang_length};
+}
diff --git a/misc/language.h b/misc/language.h
index d765e6614a..ed57e75d4d 100644
--- a/misc/language.h
+++ b/misc/language.h
@@ -20,8 +20,11 @@
 #ifndef MP_LANGUAGE_H
 #define MP_LANGUAGE_H
 
+#include "misc/bstr.h"
+
 // Result numerically higher => better match. 0 == no match.
 int mp_match_lang(char **langs, const char *lang);
 char **mp_get_user_langs(void);
+bstr mp_guess_lang_from_filename(bstr name, int *lang_start);
 
 #endif /* MP_LANGUAGE_H */
diff --git a/player/command.c b/player/command.c
index 4c7ca24db9..d16b510ed4 100644
--- a/player/command.c
+++ b/player/command.c
@@ -67,6 +67,7 @@
 #include "options/path.h"
 #include "screenshot.h"
 #include "misc/dispatch.h"
+#include "misc/language.h"
 #include "misc/node.h"
 #include "misc/thread_pool.h"
 #include "misc/thread_tools.h"
@@ -6005,7 +6006,7 @@ static void cmd_track_reload(void *p)
     struct track *nt = mpctx->tracks[nt_num];
 
     if (!nt->lang)
-        nt->lang = mp_guess_lang_from_filename(nt, nt->external_filename);
+        nt->lang = bstrto0(nt, mp_guess_lang_from_filename(bstr0(nt->external_filename), NULL));
 
     mp_switch_track(mpctx, nt->type, nt, 0);
     print_track_list(mpctx, "Reloaded:");
diff --git a/player/external_files.c b/player/external_files.c
index fd19d4fea9..9e14aba01b 100644
--- a/player/external_files.c
+++ b/player/external_files.c
@@ -24,8 +24,8 @@
 #include "common/common.h"
 #include "common/global.h"
 #include "common/msg.h"
-#include "misc/ctype.h"
 #include "misc/charset_conv.h"
+#include "misc/language.h"
 #include "options/options.h"
 #include "options/path.h"
 #include "external_files.h"
@@ -108,63 +108,6 @@ static int compare_sub_priority(const void *a, const void *b)
     return strcoll(s1->fname, s2->fname);
 }
 
-static struct bstr guess_lang_from_filename(struct bstr name, int *lang_start)
-{
-    if (name.len < 2)
-        return (struct bstr){NULL, 0};
-
-    int lang_length = 0;
-    int i = name.len - 1;
-    int suffixes_length = 0;
-
-    char delimiter = '.';
-    if (name.start[i] == ')') {
-        delimiter = '(';
-        i--;
-    }
-    if (name.start[i] == ']') {
-        delimiter = '[';
-        i--;
-    }
-
-    while (true) {
-        while (i >= 0 && mp_isalpha(name.start[i])) {
-            lang_length++;
-            i--;
-        }
-
-        // According to
-        // https://en.wikipedia.org/wiki/IETF_language_tag#Syntax_of_language_tags
-        // subtags after the first are composed of 1 to 8 letters.
-        if (lang_length < suffixes_length + 1 || lang_length > suffixes_length + 8)
-            return (struct bstr){0};
-
-        if (i >= 0 && name.start[i] == '-') {
-            lang_length++;
-            i--;
-            suffixes_length = lang_length;
-        } else {
-            break;
-        }
-    }
-
-    // The primary subtag can have 2 or 3 letters.
-    if (lang_length < suffixes_length + 2 || lang_length > suffixes_length + 3 ||
-        i == 0 || name.start[i] != delimiter)
-        return (struct bstr){0};
-
-    *lang_start = i;
-    return (struct bstr){name.start + i + 1, lang_length};
-}
-
-char *mp_guess_lang_from_filename(void* ctx, const char *filename)
-{
-    bstr filename_no_ext = bstr_strip_ext(bstr0(filename));
-    int start = 0; // only used in append_dir_subtitles()
-    char *lang = bstrto0(ctx, guess_lang_from_filename(filename_no_ext, &start));
-    return lang;
-}
-
 static void append_dir_subtitles(struct mpv_global *global, struct MPOpts *opts,
                                  struct subfn **slist, int *nsub,
                                  struct bstr path, const char *fname,
@@ -235,7 +178,7 @@ static void append_dir_subtitles(struct mpv_global *global, struct MPOpts *opts,
 
         bstr lang = {0};
         int start = 0;
-        lang = guess_lang_from_filename(tmp_fname_trim, &start);
+        lang = mp_guess_lang_from_filename(dename, &start);
         if (bstr_case_startswith(tmp_fname_trim, f_fname_trim)) {
             if (lang.len && start == f_fname_trim.len)
                 prio |= 16; // exact movie name + followed by lang
diff --git a/player/external_files.h b/player/external_files.h
index 5d42c551ae..20b37c3705 100644
--- a/player/external_files.h
+++ b/player/external_files.h
@@ -34,6 +34,5 @@ struct subfn *find_external_files(struct mpv_global *global, const char *fname,
 
 bool mp_might_be_subtitle_file(const char *filename);
 void mp_update_subtitle_exts(struct MPOpts *opts);
-char *mp_guess_lang_from_filename(void *talloc_ctx, const char *filename);
 
 #endif /* MPLAYER_FINDFILES_H */