diff --git a/biliTwin.user.js b/biliTwin.user.js
index 0246653..fde1620 100644
--- a/biliTwin.user.js
+++ b/biliTwin.user.js
@@ -2245,7 +2245,12 @@ class BiliMonkey {
                         danmuku,
                         name: index[cid].part || index[cid].index,
                         outputName: res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/) ?
-                            res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/, '')
+                            /***
+                             * see #28
+                             * Firefox lookbehind assertion not implemented https://bugzilla.mozilla.org/show_bug.cgi?id=1225665
+                             * try replace /-\d+(?=(?:\d|-|hd)*\.flv)/ => /(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/ in the future
+                             */
+                            res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/-\d+(?=(?:\d|-|hd)*\.flv)/, '')
                             : res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/) ?
                                 res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/)[0]
                                 : cid,
diff --git a/biliTwinBabelCompiled.user.js b/biliTwinBabelCompiled.user.js
index 006a213..85400d9 100644
--- a/biliTwinBabelCompiled.user.js
+++ b/biliTwinBabelCompiled.user.js
@@ -4441,7 +4441,13 @@ var BiliMonkey = function () {
                                                                 }),
                                                                 danmuku: danmuku,
                                                                 name: index[cid].part || index[cid].index,
-                                                                outputName: res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/) ? res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/, '') : res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/) ? res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/)[0] : cid,
+                                                                outputName: res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/) ?
+                                                                /***
+                                                                 * see #28
+                                                                 * Firefox lookbehind assertion not implemented https://bugzilla.mozilla.org/show_bug.cgi?id=1225665
+                                                                 * try replace /-\d+(?=(?:\d|-|hd)*\.flv)/ => /(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/ in the future
+                                                                 */
+                                                                res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/-\d+(?=(?:\d|-|hd)*\.flv)/, '') : res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/) ? res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/)[0] : cid,
                                                                 cid: cid,
                                                                 res: res
                                                             });
diff --git a/src/biliuserjs/bilimonkey.js b/src/biliuserjs/bilimonkey.js
index 487ef18..56bd5d1 100644
--- a/src/biliuserjs/bilimonkey.js
+++ b/src/biliuserjs/bilimonkey.js
@@ -697,7 +697,12 @@ class BiliMonkey {
                         danmuku,
                         name: index[cid].part || index[cid].index,
                         outputName: res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/) ?
-                            res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/, '')
+                            /***
+                             * see #28
+                             * Firefox lookbehind assertion not implemented https://bugzilla.mozilla.org/show_bug.cgi?id=1225665
+                             * try replace /-\d+(?=(?:\d|-|hd)*\.flv)/ => /(?<=\d+)-\d+(?=(?:\d|-|hd)*\.flv)/ in the future
+                             */
+                            res.durl[0].url.match(/\d+-\d+(?:\d|-|hd)*(?=\.flv)/)[0].replace(/-\d+(?=(?:\d|-|hd)*\.flv)/, '')
                             : res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/) ?
                                 res.durl[0].url.match(/\d(?:\d|-|hd)*(?=\.mp4)/)[0]
                                 : cid,