diff --git a/lib/rack/utils.rb b/lib/rack/utils.rb
index 34f43ce20..a70dcf64d 100644
--- a/lib/rack/utils.rb
+++ b/lib/rack/utils.rb
@@ -13,7 +13,7 @@ module Utils
     # version since it's faster.  (Stolen from Camping).
     def escape(s)
       s.to_s.gsub(/([^ a-zA-Z0-9_.-]+)/n) {
-        '%'+$1.unpack('H2'*$1.size).join('%').upcase
+        '%'+$1.unpack('H2'*bytesize($1)).join('%').upcase
       }.tr(' ', '+')
     end
     module_function :escape
diff --git a/test/spec_rack_utils.rb b/test/spec_rack_utils.rb
index 20abff53b..c39742997 100644
--- a/test/spec_rack_utils.rb
+++ b/test/spec_rack_utils.rb
@@ -12,6 +12,15 @@
       should.equal "q1%212%22%27w%245%267%2Fz8%29%3F%5C"
   end
 
+  specify "should escape correctly for multibyte characters" do
+    matz_name = "\xE3\x81\xBE\xE3\x81\xA4\xE3\x82\x82\xE3\x81\xA8".unpack("a*")[0] # Matsumoto
+    matz_name.force_encoding("UTF-8") if matz_name.respond_to? :force_encoding
+    Rack::Utils.escape(matz_name).should.equal '%E3%81%BE%E3%81%A4%E3%82%82%E3%81%A8'
+    matz_name_sep = "\xE3\x81\xBE\xE3\x81\xA4 \xE3\x82\x82\xE3\x81\xA8".unpack("a*")[0] # Matsu moto
+    matz_name_sep.force_encoding("UTF-8") if matz_name_sep.respond_to? :force_encoding
+    Rack::Utils.escape(matz_name_sep).should.equal '%E3%81%BE%E3%81%A4+%E3%82%82%E3%81%A8'
+  end
+
   specify "should unescape correctly" do
     Rack::Utils.unescape("fo%3Co%3Ebar").should.equal "fo<o>bar"
     Rack::Utils.unescape("a+space").should.equal "a space"