diff --git a/MozillaFirefox.changes b/MozillaFirefox.changes
index 8da05cf..d20f4a4 100644
--- a/MozillaFirefox.changes
+++ b/MozillaFirefox.changes
@@ -1,3 +1,8 @@
+-------------------------------------------------------------------
+Sun May  2 12:03:26 UTC 2021 - Wolfgang Rosenauer <wr@rosenauer.org>
+
+- add compatibility for libavcodec58_134
+
 -------------------------------------------------------------------
 Sun Apr 18 09:01:32 UTC 2021 - Wolfgang Rosenauer <wr@rosenauer.org>
 
diff --git a/mozilla-libavcodec58_91.patch b/mozilla-libavcodec58_91.patch
index 7f58c5d..8d409a4 100644
--- a/mozilla-libavcodec58_91.patch
+++ b/mozilla-libavcodec58_91.patch
@@ -1,20 +1,34 @@
-Index: firefox-78.0.2/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
-===================================================================
---- firefox-78.0.2.orig/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
-+++ firefox-78.0.2/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
-@@ -30,6 +30,7 @@ static FFmpegLibWrapper sLibAV;
+# HG changeset patch
+# Parent  e4abeadbbb7a0c63c17177f1d14ea04c77c6128e
+
+diff --git a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
+--- a/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
++++ b/dom/media/platforms/ffmpeg/FFmpegRuntimeLinker.cpp
+@@ -22,23 +22,27 @@ class FFmpegDecoderModule {
+   static already_AddRefed<PlatformDecoderModule> Create(FFmpegLibWrapper*);
+ };
+ 
+ static FFmpegLibWrapper sLibAV;
+ 
  static const char* sLibs[] = {
  // clang-format off
  #if defined(XP_DARWIN)
++  "libavcodec.58.134.dylib",
 +  "libavcodec.58.91.dylib",
    "libavcodec.58.dylib",
    "libavcodec.57.dylib",
    "libavcodec.56.dylib",
-@@ -37,6 +38,7 @@ static const char* sLibs[] = {
+   "libavcodec.55.dylib",
    "libavcodec.54.dylib",
    "libavcodec.53.dylib",
  #else
++  "libavcodec.so.58.134",
 +  "libavcodec.so.58.91",
    "libavcodec.so.58",
    "libavcodec-ffmpeg.so.58",
    "libavcodec-ffmpeg.so.57",
+   "libavcodec-ffmpeg.so.56",
+   "libavcodec.so.57",
+   "libavcodec.so.56",
+   "libavcodec.so.55",
+   "libavcodec.so.54",