diff --git a/activestorage/lib/active_storage/previewer/mupdf_previewer.rb b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
index f1f9aa85be200..a5bd3537549db 100644
--- a/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
+++ b/activestorage/lib/active_storage/previewer/mupdf_previewer.rb
@@ -4,7 +4,11 @@ module ActiveStorage
   class Previewer::MuPDFPreviewer < Previewer
     class << self
       def accept?(blob)
-        blob.content_type == "application/pdf" && mutool_exists?
+        pdf?(blob.content_type) && mutool_exists?
+      end
+
+      def pdf?(content_type)
+        Marcel::Magic.child? content_type, "application/pdf"
       end
 
       def mutool_path
diff --git a/activestorage/test/previewer/mupdf_previewer_test.rb b/activestorage/test/previewer/mupdf_previewer_test.rb
index 40b864c622e23..a15bdccee147e 100644
--- a/activestorage/test/previewer/mupdf_previewer_test.rb
+++ b/activestorage/test/previewer/mupdf_previewer_test.rb
@@ -32,6 +32,19 @@ class ActiveStorage::Previewer::MuPDFPreviewerTest < ActiveSupport::TestCase
     end
   end
 
+  test "previewing an Illustrator document that's a PDF subtype" do
+    blob = create_file_blob(fixture: "report.pdf", filename: "file.ai", content_type: "application/illustrator")
+
+    ActiveStorage::Previewer::MuPDFPreviewer.new(blob).preview do |attachable|
+      assert_equal "image/png", attachable[:content_type]
+      assert_equal "file.png", attachable[:filename]
+
+      image = MiniMagick::Image.read(attachable[:io])
+      assert_equal 612, image.width
+      assert_equal 792, image.height
+    end
+  end
+
   test "previewing a PDF that can't be previewed" do
     blob = create_file_blob(filename: "video.mp4", content_type: "application/pdf")