diff --git a/lib/sass/gem_package_importer.rb b/lib/sass/gem_package_importer.rb
index 11a25149..33c450f0 100644
--- a/lib/sass/gem_package_importer.rb
+++ b/lib/sass/gem_package_importer.rb
@@ -7,11 +7,11 @@ class GemPackageImporter
     def find_file_url(url, _canonicalize_context)
       return unless url.start_with?('pkg:')
 
-      library, _, path = url[4..].partition(/[?#]/).first.partition('/')
+      library, _, path = url[4..].partition(/[#?]/).first.partition('/')
       gem_dir = Gem::Dependency.new(library).to_spec.gem_dir
       gem_dir = "/#{gem_dir}" unless gem_dir.start_with?('/')
 
-      "file://#{gem_dir.gsub(/[?#%]/, { '?' => '%3F', '#' => '%23', '%' => '%25' })}/#{path}"
+      "file://#{gem_dir.gsub(/[#%?\\]/, { '#' => '%23', '%' => '%25', '?' => '%3F', '\\' => '%5C' })}/#{path}"
     rescue Gem::MissingSpecError
       nil
     end
diff --git a/spec/sass/gem_package_importer_spec.rb b/spec/sass/gem_package_importer_spec.rb
index cce9ebd6..9b5782cc 100644
--- a/spec/sass/gem_package_importer_spec.rb
+++ b/spec/sass/gem_package_importer_spec.rb
@@ -7,10 +7,16 @@
     require 'bundler/inline'
 
     sandbox do |dir|
+      bytes = if Gem.win_platform?
+                [*32..127] - '<>:"/\|?*'.unpack('C*')
+              else
+                (1..127)
+              end
+      parent_dir = "#{bytes.map(&:chr).join}スタイル"
       dir.write({
-                  '_test.scss' => '/* test */',
-                  '_index.scss' => '@use "test";',
-                  'test.gemspec' => <<~GEMSPEC
+                  "#{parent_dir}/_test.scss" => '/* test */',
+                  "#{parent_dir}/_index.scss" => '@use "test";',
+                  "#{parent_dir}/test.gemspec" => <<~GEMSPEC
                     Gem::Specification.new do |spec|
                       spec.name = 'test'
                       spec.summary = 'test'
@@ -22,7 +28,7 @@
                 })
 
       gemfile do
-        gem 'test', path: dir.path, require: false
+        gem 'test', path: dir.path(parent_dir), require: false
       end
 
       example.call