diff --git a/lib/capybara/selector/css.rb b/lib/capybara/selector/css.rb
index 820d288a..d4f39632 100644
--- a/lib/capybara/selector/css.rb
+++ b/lib/capybara/selector/css.rb
@@ -15,7 +15,7 @@ module Capybara
       end
 
       def self.escape_char(char)
-        char.match?(%r{[ -/:-~]}) ? "\\#{char}" : format('\\%06x', char.ord)
+        char.match?(%r{[ -/:-~]}) ? "\\#{char}" : format('\\%06<hex>x', hex: char.ord)
       end
 
       def self.split(css)
diff --git a/spec/result_spec.rb b/spec/result_spec.rb
index 1e26c7d3..43d0f6ef 100644
--- a/spec/result_spec.rb
+++ b/spec/result_spec.rb
@@ -44,9 +44,9 @@ RSpec.describe Capybara::Result do
   end
 
   it 'can be selected' do
-    expect(result.select do |element|
+    expect(result.count do |element|
       element.text.include? 't'
-    end.length).to eq(2)
+    end).to eq(2)
   end
 
   it 'can be reduced' do