diff --git a/actionpack/lib/action_dispatch/middleware/static.rb b/actionpack/lib/action_dispatch/middleware/static.rb
index fdd1bc4e69..9a92b690c7 100644
--- a/actionpack/lib/action_dispatch/middleware/static.rb
+++ b/actionpack/lib/action_dispatch/middleware/static.rb
@@ -28,7 +28,7 @@ module ActionDispatch
       paths = [path, "#{path}#{ext}", "#{path}/index#{ext}"]
 
       if match = paths.detect { |p|
-        path = File.join(@root, p)
+        path = File.join(@root, p.force_encoding('UTF-8'))
         begin
           File.file?(path) && File.readable?(path)
         rescue SystemCallError
diff --git a/actionpack/test/dispatch/static_test.rb b/actionpack/test/dispatch/static_test.rb
index 288a2084f6..f153030675 100644
--- a/actionpack/test/dispatch/static_test.rb
+++ b/actionpack/test/dispatch/static_test.rb
@@ -2,6 +2,16 @@ require 'abstract_unit'
 require 'zlib'
 
 module StaticTests
+  def setup
+    @default_internal_encoding = Encoding.default_internal
+    @default_external_encoding = Encoding.default_external
+  end
+
+  def teardown
+    Encoding.default_internal = @default_internal_encoding
+    Encoding.default_external = @default_external_encoding
+  end
+
   def test_serves_dynamic_content
     assert_equal "Hello, World!", get("/nofile").body
   end
@@ -10,6 +20,16 @@ module StaticTests
     assert_equal "Hello, World!", get("/doorkeeper%E3E4").body
   end
 
+  def test_handles_urls_with_ascii_8bit
+    assert_equal "Hello, World!", get("/doorkeeper%E3E4".force_encoding('ASCII-8BIT')).body
+  end
+
+  def test_handles_urls_with_ascii_8bit_on_win_31j
+    Encoding.default_internal = "Windows-31J"
+    Encoding.default_external = "Windows-31J"
+    assert_equal "Hello, World!", get("/doorkeeper%E3E4".force_encoding('ASCII-8BIT')).body
+  end
+
   def test_sets_cache_control
     response = get("/index.html")
     assert_html "/index.html", response
@@ -208,6 +228,7 @@ class StaticTest < ActiveSupport::TestCase
   }
 
   def setup
+    super
     @root = "#{FIXTURE_LOAD_PATH}/public"
     @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end
@@ -237,6 +258,7 @@ end
 
 class StaticEncodingTest < StaticTest
   def setup
+    super
     @root = "#{FIXTURE_LOAD_PATH}/公共"
     @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end