diff --git a/lib/uri/common.rb b/lib/uri/common.rb
index 621353093d..576b407de9 100644
--- a/lib/uri/common.rb
+++ b/lib/uri/common.rb
@@ -31,11 +31,6 @@ module URI
     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|
diff --git a/test/uri/test_common.rb b/test/uri/test_common.rb
index b1e3b2be66..e96f819968 100644
--- a/test/uri/test_common.rb
+++ b/test/uri/test_common.rb
@@ -40,6 +40,7 @@ class URI::TestCommon < Test::Unit::TestCase
     assert defined?(URI::REGEXP)
     assert defined?(URI::PATTERN)
     assert defined?(URI::PATTERN::ESCAPED)
+    assert defined?(URI::REGEXP::PATTERN::IPV6ADDR)
 
     URI.parser = URI::RFC3986_PARSER