diff --git a/CHANGELOG b/CHANGELOG
index b0e9e13..4f228f5 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+== 8.4.2 2026-04-01
+
+Fixes:
+* Correctly detect the file extension for old-style MOV files (no ftyp box).
+
 == 8.4.1 2026-04-01
 
 Fixes:
diff --git a/lib/ffmpeg/media.rb b/lib/ffmpeg/media.rb
index b6007b6..2ee8bfe 100644
--- a/lib/ffmpeg/media.rb
+++ b/lib/ffmpeg/media.rb
@@ -83,11 +83,11 @@ def initialize(message, output)
       when /\basf_o\b/     then '.asf'
       when /\b(mov|mp4)\b/
         case major_brand
-        when /\Aqt\b/i  then '.mov'
-        when /\Am4a\b/i then '.m4a'
-        when /\Am4v\b/i then '.m4v'
-        when /\Am4s\b/i then '.m4s'
-        else                 '.mp4'
+        when nil, /\Aqt\b/i then '.mov'
+        when /\Am4a\b/i     then '.m4a'
+        when /\Am4v\b/i     then '.m4v'
+        when /\Am4s\b/i     then '.m4s'
+        else                     '.mp4'
         end
       when /\bmatroska\b/
         if streams
diff --git a/lib/ffmpeg/version.rb b/lib/ffmpeg/version.rb
index fe0c61e..1244a32 100644
--- a/lib/ffmpeg/version.rb
+++ b/lib/ffmpeg/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module FFMPEG
-  VERSION = '8.4.1'
+  VERSION = '8.4.2'
 end
diff --git a/spec/ffmpeg/media_spec.rb b/spec/ffmpeg/media_spec.rb
index dc97229..72dab29 100644
--- a/spec/ffmpeg/media_spec.rb
+++ b/spec/ffmpeg/media_spec.rb
@@ -609,6 +609,16 @@ module FFMPEG
         end
       end
 
+      context 'when the media is an old-style QuickTime MOV without an ftyp box' do
+        let(:path) { fixture_media_file('rotated@0.mov') }
+
+        before { allow(subject).to receive(:major_brand).and_return(nil) }
+
+        it 'returns .mov' do
+          expect(subject.extname).to eq('.mov')
+        end
+      end
+
       context 'when the media is a WAV' do
         let(:path) { fixture_media_file('hello.wav') }