diff --git a/lib/wicked_pdf/wicked_pdf_helper/assets.rb b/lib/wicked_pdf/wicked_pdf_helper/assets.rb
index 77163265..686d2d0c 100644
--- a/lib/wicked_pdf/wicked_pdf_helper/assets.rb
+++ b/lib/wicked_pdf/wicked_pdf_helper/assets.rb
@@ -202,13 +202,32 @@ def find_asset(path)
         elsif defined?(Propshaft::Assembly) && Rails.application.assets.is_a?(Propshaft::Assembly)
           PropshaftAsset.new(Rails.application.assets.load_path.find(path))
         elsif Rails.application.respond_to?(:assets_manifest)
-          asset_path = File.join(Rails.application.assets_manifest.dir, Rails.application.assets_manifest.assets[path])
+          relative_asset_path = get_asset_path_from_manifest(path)
+          return unless relative_asset_path
+
+          asset_path = File.join(Rails.application.assets_manifest.dir, relative_asset_path)
           LocalAsset.new(asset_path) if File.file?(asset_path)
         else
           SprocketsEnvironment.find_asset(path, :base_path => Rails.application.root.to_s)
         end
       end
 
+      def get_asset_path_from_manifest(path)
+        assets = Rails.application.assets_manifest.assets
+
+        if File.extname(path).empty?
+          assets.find do |asset, _v|
+            directory = File.dirname(asset)
+            asset_path = File.basename(asset, File.extname(asset))
+            asset_path = File.join(directory, asset_path) if directory != '.'
+
+            asset_path == path
+          end&.last
+        else
+          assets[path]
+        end
+      end
+
       # will prepend a http or default_protocol to a protocol relative URL
       # or when no protcol is set.
       def prepend_protocol(source)
diff --git a/test/fixtures/subdirectory/nested.js b/test/fixtures/subdirectory/nested.js
new file mode 100644
index 00000000..700bfaac
--- /dev/null
+++ b/test/fixtures/subdirectory/nested.js
@@ -0,0 +1 @@
+// Nested js
diff --git a/test/functional/wicked_pdf_helper_assets_test.rb b/test/functional/wicked_pdf_helper_assets_test.rb
index 2b8368b1..e4df813a 100644
--- a/test/functional/wicked_pdf_helper_assets_test.rb
+++ b/test/functional/wicked_pdf_helper_assets_test.rb
@@ -11,6 +11,10 @@ class WickedPdfHelperAssetsTest < ActionView::TestCase
 
   teardown do
     WickedPdf.config = @saved_config
+
+    # @see freerange/mocha#331
+    Rails.application.unstub(:assets)
+    Rails.application.unstub(:assets_manifest)
   end
 
   if Rails::VERSION::MAJOR > 3 || (Rails::VERSION::MAJOR == 3 && Rails::VERSION::MINOR > 0)
@@ -18,12 +22,61 @@ class WickedPdfHelperAssetsTest < ActionView::TestCase
       assert_match %r{data:text\/css;base64,.+}, wicked_pdf_asset_base64('wicked.css')
     end
 
+    test 'wicked_pdf_asset_base64 works without file extension when using sprockets' do
+      assert_match %r{data:application\/javascript;base64,.+}, wicked_pdf_asset_base64('wicked')
+    end
+
+    test 'wicked_pdf_asset_base64 works with nested files and without file extension when using sprockets' do
+      assert_match %r{data:application\/javascript;base64,.+}, wicked_pdf_asset_base64('subdirectory/nested')
+    end
+
+    test 'wicked_pdf_asset_base64 works without file extension when using asset manifest' do
+      stub_manifest = OpenStruct.new(
+        :dir => Rails.root.join('app/assets'),
+        :assets => { 'wicked.css' => 'stylesheets/wicked.css', 'wicked.js' => 'javascripts/wicked.js' }
+      )
+      Rails.application.stubs(:assets).returns(nil)
+      Rails.application.stubs(:assets_manifest).returns(stub_manifest)
+
+      assert_match %r{data:text\/css;base64,.+}, wicked_pdf_asset_base64('wicked')
+    end
+
+    test 'wicked_pdf_asset_base64 works with nested files and without file extension when using asset manifest' do
+      stub_manifest = OpenStruct.new(
+        :dir => Rails.root.join('app/assets'),
+        :assets => { 'subdirectory/nested.js' => 'javascripts/subdirectory/nested.js' }
+      )
+      Rails.application.stubs(:assets).returns(nil)
+      Rails.application.stubs(:assets_manifest).returns(stub_manifest)
+
+      assert_match %r{data:text\/javascript;base64,.+}, wicked_pdf_asset_base64('subdirectory/nested')
+    end
+
     test 'wicked_pdf_stylesheet_link_tag should inline the stylesheets passed in' do
       Rails.configuration.assets.expects(:compile => true)
       assert_equal "<style type='text/css'>/* Wicked styles */\n\n</style>",
                    wicked_pdf_stylesheet_link_tag('wicked')
     end
 
+    test 'wicked_pdf_stylesheet_link_tag should work without file extension when using sprockets' do
+      Rails.configuration.assets.expects(:compile => true)
+      assert_equal "<style type='text/css'>/* Wicked styles */\n\n</style>",
+                   wicked_pdf_stylesheet_link_tag('wicked')
+    end
+
+    test 'wicked_pdf_stylesheet_link_tag should work without file extension when using asset manifest' do
+      stub_manifest = OpenStruct.new(
+        :dir => Rails.root.join('app/assets'),
+        :assets => { 'wicked.css' => 'stylesheets/wicked.css', 'wicked.js' => 'javascripts/wicked.js' }
+      )
+
+      Rails.application.stubs(:assets).returns(nil)
+      Rails.application.stubs(:assets_manifest).returns(stub_manifest)
+
+      assert_equal "<style type='text/css'>/* Wicked styles */\n</style>",
+                   wicked_pdf_stylesheet_link_tag('wicked')
+    end
+
     test 'wicked_pdf_stylesheet_link_tag should raise if the stylesheet is not available and config is set' do
       Rails.configuration.assets.expects(:compile => true)
       WickedPdf.config[:raise_on_missing_assets] = true
@@ -60,6 +113,21 @@ class WickedPdfHelperAssetsTest < ActionView::TestCase
                    wicked_pdf_stylesheet_link_tag('https://www.example.com/wicked.css')
     end
 
+    test 'wicked_pdf_stylesheet_link_tag should inline the stylesheets passed in when assets are remote and using asset manifest' do
+      stub_manifest = OpenStruct.new(
+        :dir => Rails.root.join('app/assets'),
+        :assets => { 'wicked.css' => 'stylesheets/wicked.css', 'wicked.js' => 'javascripts/wicked.js' }
+      )
+
+      Rails.application.stubs(:assets).returns(nil)
+      Rails.application.stubs(:assets_manifest).returns(stub_manifest)
+
+      stub_request(:get, 'https://www.example.com/wicked.css').to_return(:status => 200, :body => '/* Wicked styles */')
+      expects(:precompiled_or_absolute_asset? => true).twice
+      assert_equal "<style type='text/css'>/* Wicked styles */</style>",
+                   wicked_pdf_stylesheet_link_tag('https://www.example.com/wicked.css')
+    end
+
     test 'wicked_pdf_stylesheet_link_tag should raise if remote assets are not available and config is set' do
       WickedPdf.config[:raise_on_missing_assets] = true
       stub_request(:get, 'https://www.example.com/wicked.css').to_return(:status => 404, :body => 'File not found')
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 4820d5b2..26bb92df 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -27,6 +27,11 @@
   source = File.read('test/fixtures/wicked.js')
   File.open(destination, 'w') { |f| f.write(source) }
 
+  Dir.mkdir(js_dir.join('subdirectory')) unless File.directory?(js_dir.join('subdirectory'))
+  destination = js_dir.join('subdirectory/nested.js')
+  source = File.read('test/fixtures/subdirectory/nested.js')
+  File.open(destination, 'w') { |f| f.write(source) }
+
   config_dir = assets_dir.join('config')
   Dir.mkdir(config_dir) unless File.directory?(config_dir)
   source = File.read('test/fixtures/manifest.js')