diff --git a/lib/rack/utils.rb b/lib/rack/utils.rb
index 6017d0e..33528c6 100644
--- a/lib/rack/utils.rb
+++ b/lib/rack/utils.rb
@@ -36,7 +36,9 @@ module Rack
       (qs || '').split(/[#{d}] */n).each do |p|
         k, v = unescape(p).split('=', 2)
 
-        if cur = params[k]
+        if k.include?('[')
+          normalize_params(params, k, v)
+        elsif cur = params[k]
           if cur.class == Array
             params[k] << v
           else
@@ -51,6 +53,40 @@ module Rack
     end
     module_function :parse_query
 
+    def normalize_params(params, name, val = nil)
+      name =~ %r([\[\]]*([^\[\]]+)\]*)
+      key = $1 || ''
+      after = $' || ''
+
+      if after == ""
+        params[key] = val
+      elsif after == "[]"
+        (params[key] ||= []) << val
+      elsif after =~ %r(^\[\]\[([^\[\]]+)\]$)
+        child_key = $1
+        params[key] ||= []
+        if params[key].last.is_a?(Hash) && !params[key].last.key?(child_key)
+          params[key].last.update(child_key => val)
+        else
+          params[key] << { child_key => val }
+        end
+      elsif after =~ %r(^\[\](.+)$)
+        child_key = $1
+        params[key] ||= []
+        if params[key].last.is_a?(Hash) && !params[key].last.key?(child_key)
+          normalize_params(params[key].last, child_key, val)
+        else
+          params[key] << normalize_params({}, child_key, val)
+        end
+      else
+        params[key] ||= {}
+        params[key] = normalize_params(params[key], after, val)
+      end
+
+      return params
+    end
+    module_function :normalize_params
+
     def build_query(params)
       params.map { |k, v|
         if v.class == Array
diff --git a/test/spec_rack_utils.rb b/test/spec_rack_utils.rb
index f16ac4c..c999f22 100644
--- a/test/spec_rack_utils.rb
+++ b/test/spec_rack_utils.rb
@@ -28,6 +28,31 @@ context "Rack::Utils" do
       should.equal "foo" => "1", "bar" => "2"
     Rack::Utils.parse_query("my+weird+field=q1%212%22%27w%245%267%2Fz8%29%3F").
       should.equal "my weird field" => "q1!2\"'w$5&7/z8)?"
+
+    Rack::Utils.parse_query("x[y][z]=10").
+      should.equal "x" => {"y" => {"z" => "10"}}
+    Rack::Utils.parse_query("x[y][z][]=10").
+      should.equal "x" => {"y" => {"z" => ["10"]}}
+    Rack::Utils.parse_query("x[y][z][]=10&x[y][z][]=5").
+      should.equal "x" => {"y" => {"z" => ["10", "5"]}}
+    Rack::Utils.parse_query("x[y][][z]=10").
+      should.equal "x" => {"y" => [{"z" => "10"}]}
+    Rack::Utils.parse_query("x[y][][z]=10&x[y][][w]=10").
+      should.equal "x" => {"y" => [{"z" => "10", "w" => "10"}]}
+    Rack::Utils.parse_query("x[y][][v][w]=10").
+      should.equal "x" => {"y" => [{"v" => {"w" => "10"}}]}
+    Rack::Utils.parse_query("x[y][][z]=10&x[y][][v][w]=10").
+      should.equal "x" => {"y" => [{"z" => "10", "v" => {"w" => "10"}}]}
+    Rack::Utils.parse_query("x[y][][z]=10&x[y][][z]=20").
+      should.equal "x" => {"y" => [{"z" => "10"}, {"z" => "20"}]}
+    Rack::Utils.parse_query("x[y][][z]=10&x[y][][w]=a&x[y][][z]=20&x[y][][w]=b").
+      should.equal "x" => {"y" => [{"z" => "10", "w" => "a"}, {"z" => "20", "w" => "b"}]}
+    Rack::Utils.parse_query("foo=bar&baz=").
+      should.equal "foo" => "bar", "baz" => ""
+    Rack::Utils.parse_query("foo=bar&baz[]=1&baz[]=2&baz[]=3").
+      should.equal "foo" => "bar", "baz" => ["1", "2", "3"]
+    Rack::Utils.parse_query("foo[]=bar&baz[]=1&baz[]=2&baz[]=3").
+      should.equal "foo" => ["bar"], "baz" => ["1", "2", "3"]
   end
 
   specify "should build query strings correctly" do