diff --git a/app/models/media_asset.rb b/app/models/media_asset.rb
index 074bd5458..19b6a4076 100644
--- a/app/models/media_asset.rb
+++ b/app/models/media_asset.rb
@@ -28,6 +28,7 @@ class MediaAsset < ApplicationRecord
     self.file_size = media_file.file_size
     self.image_width = media_file.width
     self.image_height = media_file.height
+    self.duration = media_file.duration
     self.media_metadata = MediaMetadata.new(file: media_file)
   end
 end
diff --git a/script/fixes/079_fix_duration.rb b/script/fixes/079_fix_duration.rb
new file mode 100755
index 000000000..19ad10ee6
--- /dev/null
+++ b/script/fixes/079_fix_duration.rb
@@ -0,0 +1,15 @@
+#!/usr/bin/env ruby
+
+require_relative "../../config/environment"
+
+tags = ENV.fetch("TAGS", "animated")
+posts = Post.system_tag_match(tags)
+assets = posts.joins(:media_asset).where(media_asset: { duration: nil })
+
+posts.find_each do |post|
+  media_file = MediaFile.open(post.file(:original), frame_data: post.pixiv_ugoira_frame_data&.data)
+  post.media_asset.update!(duration: media_file.duration)
+  puts "id=#{post.id}, md5=#{post.md5}, ext=#{post.file_ext}, duration=#{post.media_asset.duration}"
+rescue StandardError => e
+  puts "error[id=#{post.id}]: #{e}"
+end