diff --git a/pkgs/applications/video/mkvtoolnix/default.nix b/pkgs/applications/video/mkvtoolnix/default.nix
index 7cffcd923ff7..0f271dd889e8 100644
--- a/pkgs/applications/video/mkvtoolnix/default.nix
+++ b/pkgs/applications/video/mkvtoolnix/default.nix
@@ -122,6 +122,11 @@ stdenv.mkDerivation rec {
 
   dontWrapQtApps = true;
 
+  # Avoid Qt 5.12 problem on Big Sur: https://bugreports.qt.io/browse/QTBUG-87014
+  qtWrapperArgs = lib.optionals stdenv.isDarwin [
+    "--set QT_MAC_WANTS_LAYER 1"
+  ];
+
   postFixup = optionalString withGUI ''
     wrapQtApp $out/bin/mkvtoolnix-gui
   '';
@@ -131,7 +136,6 @@ stdenv.mkDerivation rec {
     homepage = "https://mkvtoolnix.download/";
     license = licenses.gpl2Only;
     maintainers = with maintainers; [ codyopel rnhmjoj ];
-    platforms = platforms.linux
-      ++ optionals (!withGUI) platforms.darwin;
+    platforms = platforms.unix;
   };
 }