diff --git a/lib/uri/common.rb b/lib/uri/common.rb
index faf75f0..b5b6177 100644
--- a/lib/uri/common.rb
+++ b/lib/uri/common.rb
@@ -13,24 +13,37 @@
 require_relative "rfc3986_parser"
 
 module URI
-  include RFC2396_REGEXP
+  RFC2396_PARSER = RFC2396_Parser.new
+  Ractor.make_shareable(RFC2396_PARSER) if defined?(Ractor)
 
-  REGEXP = RFC2396_REGEXP
-  Parser = RFC2396_Parser
   RFC3986_PARSER = RFC3986_Parser.new
   Ractor.make_shareable(RFC3986_PARSER) if defined?(Ractor)
 
-  # URI::Parser.new
-  DEFAULT_PARSER = Parser.new
-  DEFAULT_PARSER.pattern.each_pair do |sym, str|
-    unless REGEXP::PATTERN.const_defined?(sym)
-      REGEXP::PATTERN.const_set(sym, str)
+  DEFAULT_PARSER = RFC3986_PARSER
+  Ractor.make_shareable(DEFAULT_PARSER) if defined?(Ractor)
+
+  def self.parser=(parser = RFC3986_PARSER)
+    remove_const(:Parser) if defined?(Parser)
+    const_set("Parser", parser.class)
+
+    remove_const(:REGEXP) if defined?(REGEXP)
+    remove_const(:PATTERN) if defined?(PATTERN)
+    if Parser == RFC2396_Parser
+      const_set("REGEXP", URI::RFC2396_REGEXP)
+      const_set("PATTERN", URI::RFC2396_REGEXP::PATTERN)
+      Parser.new.pattern.each_pair do |sym, str|
+        unless REGEXP::PATTERN.const_defined?(sym)
+          REGEXP::PATTERN.const_set(sym, str)
+        end
+      end
+    end
+
+    Parser.new.regexp.each_pair do |sym, str|
+      remove_const(sym) if const_defined?(sym)
+      const_set(sym, str)
     end
   end
-  DEFAULT_PARSER.regexp.each_pair do |sym, str|
-    const_set(sym, str)
-  end
-  Ractor.make_shareable(DEFAULT_PARSER) if defined?(Ractor)
+  self.parser = RFC3986_PARSER
 
   module Util # :nodoc:
     def make_components_hash(klass, array_hash)
diff --git a/lib/uri/rfc3986_parser.rb b/lib/uri/rfc3986_parser.rb
index 092a1ac..529ecfa 100644
--- a/lib/uri/rfc3986_parser.rb
+++ b/lib/uri/rfc3986_parser.rb
@@ -135,12 +135,31 @@ def parse(uri) # :nodoc:
       URI.for(*self.split(uri), self)
     end
 
-
     def join(*uris) # :nodoc:
       uris[0] = convert_to_uri(uris[0])
       uris.inject :merge
     end
 
+    # Compatibility for RFC2396 parser
+    def extract(str, schemes = nil, &block) # :nodoc:
+      RFC2396_PARSER.extract(str, schemes, &block)
+    end
+
+    # Compatibility for RFC2396 parser
+    def make_regexp(schemes = nil) # :nodoc:
+      RFC2396_PARSER.make_regexp(schemes)
+    end
+
+    # Compatibility for RFC2396 parser
+    def escape(str, unsafe = nil) # :nodoc:
+      unsafe ? RFC2396_PARSER.escape(str, unsafe) : RFC2396_PARSER.escape(str)
+    end
+
+    # Compatibility for RFC2396 parser
+    def unescape(str, escaped = nil) # :nodoc:
+      escaped ? RFC2396_PARSER.unescape(str, escaped) : RFC2396_PARSER.unescape(str)
+    end
+
     @@to_s = Kernel.instance_method(:to_s)
     if @@to_s.respond_to?(:bind_call)
       def inspect
diff --git a/test/uri/test_common.rb b/test/uri/test_common.rb
index 1df19e6..aa9c689 100644
--- a/test/uri/test_common.rb
+++ b/test/uri/test_common.rb
@@ -10,6 +10,27 @@ def setup
   def teardown
   end
 
+  def test_parser_switch
+    assert_equal(URI::Parser, URI::RFC3986_Parser)
+    refute defined?(URI::REGEXP)
+    refute defined?(URI::PATTERN)
+
+    URI.parser = URI::RFC2396_PARSER
+
+    assert_equal(URI::Parser, URI::RFC2396_Parser)
+    assert defined?(URI::REGEXP)
+    assert defined?(URI::PATTERN)
+    assert defined?(URI::PATTERN::ESCAPED)
+
+    URI.parser = URI::RFC3986_PARSER
+
+    assert_equal(URI::Parser, URI::RFC3986_Parser)
+    refute defined?(URI::REGEXP)
+    refute defined?(URI::PATTERN)
+  ensure
+    URI.parser = URI::RFC3986_PARSER
+  end
+
   def test_extract
     EnvUtil.suppress_warning do
       assert_equal(['http://example.com'],
diff --git a/test/uri/test_parser.rb b/test/uri/test_parser.rb
index 75c02fe..9105d47 100644
--- a/test/uri/test_parser.rb
+++ b/test/uri/test_parser.rb
@@ -8,8 +8,8 @@ def uri_to_ary(uri)
   end
 
   def test_inspect
-    assert_match(/URI::RFC2396_Parser/, URI::Parser.new.inspect)
-    assert_match(/URI::RFC3986_Parser/, URI::RFC3986_Parser.new.inspect)
+    assert_match(/URI::RFC2396_Parser/, URI::RFC2396_Parser.new.inspect)
+    assert_match(/URI::RFC3986_Parser/, URI::Parser.new.inspect)
   end
 
   def test_compare
@@ -33,7 +33,9 @@ def test_compare
     assert(!u2.equal?(u3))
   end
 
-  def test_parse
+  def test_parse_rfc2396_parser
+    URI.parser = URI::RFC2396_PARSER
+
     escaped = URI::REGEXP::PATTERN::ESCAPED
     hex = URI::REGEXP::PATTERN::HEX
     p1 = URI::Parser.new(:ESCAPED => "(?:#{escaped}|%u[#{hex}]{4})")
@@ -43,6 +45,8 @@ def test_parse
     u1.path = '/%uDCBA'
     assert_equal(['http', nil, 'a', URI::HTTP.default_port, '/%uDCBA', nil, nil],
 		 uri_to_ary(u1))
+  ensure
+    URI.parser = URI::DEFAULT_PARSER
   end
 
   def test_parse_query_pct_encoded