diff --git a/lib/ruby/1.9/uri/common.rb b/lib/ruby/1.9/uri/common.rb
index ed8556c9760..264fa053ed6 100644
--- a/lib/ruby/1.9/uri/common.rb
+++ b/lib/ruby/1.9/uri/common.rb
@@ -717,7 +717,22 @@ def self.regexp(schemes = nil)
   end
 
   TBLENCWWWCOMP_ = {} # :nodoc:
+  256.times do |i|
+    TBLENCWWWCOMP_[i.chr] = '%%%02X' % i
+  end
+  TBLENCWWWCOMP_[' '] = '+'
+  TBLENCWWWCOMP_.freeze
   TBLDECWWWCOMP_ = {} # :nodoc:
+  256.times do |i|
+    h, l = i>>4, i&15
+    TBLDECWWWCOMP_['%%%X%X' % [h, l]] = i.chr
+    TBLDECWWWCOMP_['%%%x%X' % [h, l]] = i.chr
+    TBLDECWWWCOMP_['%%%X%x' % [h, l]] = i.chr
+    TBLDECWWWCOMP_['%%%x%x' % [h, l]] = i.chr
+  end
+  TBLDECWWWCOMP_['+'] = ' '
+  TBLDECWWWCOMP_.freeze
+
   HTML5ASCIIINCOMPAT = [Encoding::UTF_7, Encoding::UTF_16BE, Encoding::UTF_16LE,
     Encoding::UTF_32BE, Encoding::UTF_32LE] # :nodoc:
 
@@ -730,18 +745,6 @@ def self.regexp(schemes = nil)
   #
   # See URI.decode_www_form_component, URI.encode_www_form
   def self.encode_www_form_component(str)
-    if TBLENCWWWCOMP_.empty?
-      tbl = {}
-      256.times do |i|
-        tbl[i.chr] = '%%%02X' % i
-      end
-      tbl[' '] = '+'
-      begin
-        TBLENCWWWCOMP_.replace(tbl)
-        TBLENCWWWCOMP_.freeze
-      rescue
-      end
-    end
     str = str.to_s
     if HTML5ASCIIINCOMPAT.include?(str.encoding)
       str = str.encode(Encoding::UTF_8)
@@ -759,22 +762,6 @@ def self.encode_www_form_component(str)
   #
   # See URI.encode_www_form_component, URI.decode_www_form
   def self.decode_www_form_component(str, enc=Encoding::UTF_8)
-    if TBLDECWWWCOMP_.empty?
-      tbl = {}
-      256.times do |i|
-        h, l = i>>4, i&15
-        tbl['%%%X%X' % [h, l]] = i.chr
-        tbl['%%%x%X' % [h, l]] = i.chr
-        tbl['%%%X%x' % [h, l]] = i.chr
-        tbl['%%%x%x' % [h, l]] = i.chr
-      end
-      tbl['+'] = ' '
-      begin
-        TBLDECWWWCOMP_.replace(tbl)
-        TBLDECWWWCOMP_.freeze
-      rescue
-      end
-    end
     raise ArgumentError, "invalid %-encoding (#{str})" unless /\A(?:%\h\h|[^%]+)*\z/ =~ str
     str.gsub(/\+|%\h\h/, TBLDECWWWCOMP_).force_encoding(enc)
   end