diff --git a/lib/rack/test/utils.rb b/lib/rack/test/utils.rb
index a79a8e7..d1f7456 100644
--- a/lib/rack/test/utils.rb
+++ b/lib/rack/test/utils.rb
@@ -6,9 +6,16 @@ module Utils # :nodoc:
       include Rack::Utils
       extend self
 
+      class << self
+        attr_accessor :override_build_nested_query
+      end
+      self.override_build_nested_query = false
+
       # Build a query string for the given value and prefix. The value
       # can be an array or hash of parameters.
       def build_nested_query(value, prefix = nil)
+        return super if Rack::Test::Utils.override_build_nested_query
+
         case value
         when Array
           if value.empty?
diff --git a/spec/rack/test/utils_spec.rb b/spec/rack/test/utils_spec.rb
index 9cb3670..090276d 100644
--- a/spec/rack/test/utils_spec.rb
+++ b/spec/rack/test/utils_spec.rb
@@ -58,6 +58,21 @@
     input = { collection: [] }
     build_nested_query(input).must_equal 'collection[]='
   end
+
+  it 'percent encodes brackets with override_build_nested_query' do
+    original = Rack::Test::Utils.override_build_nested_query
+    Rack::Test::Utils.override_build_nested_query = true
+    begin
+      query = if Gem::Version.new(Rack.release) < Gem::Version.new("3.1")
+                'a[b]=c'
+              else
+                'a%5Bb%5D=c'
+              end
+      build_nested_query({"a" => { "b" => "c" }}).must_equal query
+    ensure
+      Rack::Test::Utils.override_build_nested_query = original
+    end
+  end
 end
 
 describe 'Rack::Test::Utils.build_multipart' do