diff --git a/.minitestfailures b/.minitestfailures
new file mode 100644
index 00000000..0637a088
--- /dev/null
+++ b/.minitestfailures
@@ -0,0 +1 @@
+[]
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0ea6b8e7..99d988ea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+- Reuse the detected browser for bot detection instead of parsing the user agent
+  twice. Custom bot matchers now receive that browser instead of a
+  `Browser::Unknown` built from the downcased user agent.
+
 ## 6.2.0
 
 - Add `Browser::Base#epiphany?`.
diff --git a/lib/browser/base.rb b/lib/browser/base.rb
index b6c551df..17847748 100644
--- a/lib/browser/base.rb
+++ b/lib/browser/base.rb
@@ -7,7 +7,7 @@ class Base
     attr_reader :ua
 
     def initialize(ua, accept_language: nil)
-      validate_size(:user_agent, ua.to_s)
+      validate_size(:user_agent, ua.to_s, Browser.user_agent_size_limit)
 
       @ua = ua
       @accept_language_raw = accept_language.to_s
@@ -21,7 +21,11 @@ def meta
     # Return an array with all preferred languages that this browser accepts.
     def accept_language
       @accept_language ||= begin
-        validate_size(:accept_language, @accept_language_raw)
+        validate_size(
+          :accept_language,
+          @accept_language_raw,
+          Browser.accept_language_size_limit
+        )
         AcceptLanguage.parse(@accept_language_raw)
       end
     end
@@ -44,7 +48,7 @@ def platform
 
     # Return the bot info.
     def bot
-      @bot ||= Bot.new(ua)
+      @bot ||= Bot.new(ua, browser: self)
     end
 
     # Detect if current user agent is from a bot.
@@ -273,9 +277,8 @@ def epiphany?(expected_version = nil)
       instance_of?(Epiphany) && detect_version?(full_version, expected_version)
     end
 
-    private def validate_size(subject, input)
+    private def validate_size(subject, input, size_limit)
       actual_bytesize = input.bytesize
-      size_limit = Browser.public_send(:"#{subject}_size_limit")
 
       return if actual_bytesize < size_limit
 
diff --git a/lib/browser/bot.rb b/lib/browser/bot.rb
index cd0051fc..bcb6ef4a 100644
--- a/lib/browser/bot.rb
+++ b/lib/browser/bot.rb
@@ -40,9 +40,9 @@ def self.why?(ua)
 
     attr_reader :ua, :browser
 
-    def initialize(ua)
+    def initialize(ua, browser: nil)
       @ua = ua.downcase.strip
-      @browser = Browser.new(@ua)
+      @browser = browser || Browser.new(@ua)
     end
 
     def bot?
diff --git a/test/unit/bots_test.rb b/test/unit/bots_test.rb
index 53919806..e7f8f390 100644
--- a/test/unit/bots_test.rb
+++ b/test/unit/bots_test.rb
@@ -93,6 +93,20 @@ class BotsTest < Minitest::Test
     assert_equal "Generic Bot", browser.bot.name
   end
 
+  test "passes the detected browser to custom bot matchers" do
+    matched_browsers = []
+    Browser::Bot.matchers << lambda {|_ua, browser|
+      matched_browsers << browser
+      false
+    }
+    browser = Browser.new(Browser["CHROME"])
+
+    refute browser.bot?
+    assert_same browser, matched_browsers.last
+  ensure
+    Browser::Bot.matchers.pop
+  end
+
   %w[
     content-fetcher
     content-crawler