diff --git a/Library/Homebrew/compat/compatibility.rb b/Library/Homebrew/compat/compatibility.rb
index 51969330f7..aee5da63fb 100644
--- a/Library/Homebrew/compat/compatibility.rb
+++ b/Library/Homebrew/compat/compatibility.rb
@@ -202,22 +202,15 @@ end
 
 # MD5 support
 class Formula
-  def self.md5(val=nil)
-    unless val.nil?
-      @stable ||= SoftwareSpec.new
-      @stable.md5(val)
-    end
-    return @stable ? @stable.md5 : @md5
+  def self.md5(val)
+    @stable ||= SoftwareSpec.new
+    @stable.md5(val)
   end
 end
 
 class SoftwareSpec
-  def md5(val=nil)
-    if val.nil?
-      @checksum if checksum.nil? or @checksum.hash_type == :md5
-    else
-      @checksum = Checksum.new(:md5, val)
-    end
+  def md5(val)
+    @checksum = Checksum.new(:md5, val)
   end
 end
 
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 77b1fabdb0..490b517a6a 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -677,12 +677,9 @@ private
 
     Checksum::TYPES.each do |cksum|
       class_eval <<-EOS, __FILE__, __LINE__ + 1
-        def #{cksum}(val=nil)
-          unless val.nil?
-            @stable ||= SoftwareSpec.new
-            @stable.#{cksum}(val)
-          end
-          return @stable ? @stable.#{cksum} : @#{cksum}
+        def #{cksum}(val)
+          @stable ||= SoftwareSpec.new
+          @stable.#{cksum}(val)
         end
       EOS
     end
diff --git a/Library/Homebrew/formula_support.rb b/Library/Homebrew/formula_support.rb
index 4c044c53a4..40bb561b82 100644
--- a/Library/Homebrew/formula_support.rb
+++ b/Library/Homebrew/formula_support.rb
@@ -33,12 +33,8 @@ class SoftwareSpec
   # The methods that follow are used in the block-form DSL spec methods
   Checksum::TYPES.each do |cksum|
     class_eval <<-EOS, __FILE__, __LINE__ + 1
-      def #{cksum}(val=nil)
-        if val.nil?
-          @checksum if @checksum.nil? or @checksum.hash_type == :#{cksum}
-        else
-          @checksum = Checksum.new(:#{cksum}, val)
-        end
+      def #{cksum}(val)
+        @checksum = Checksum.new(:#{cksum}, val)
       end
     EOS
   end
@@ -94,11 +90,9 @@ class Bottle < SoftwareSpec
   # a Hash, which indicates the platform the checksum applies on.
   Checksum::TYPES.each do |cksum|
     class_eval <<-EOS, __FILE__, __LINE__ + 1
-      def #{cksum}(val=nil)
+      def #{cksum}(val)
         @#{cksum} ||= Hash.new
         case val
-        when nil
-          @#{cksum}[MacOS.cat]
         when Hash
           key, value = val.shift
           @#{cksum}[value] = Checksum.new(:#{cksum}, key)
diff --git a/Library/Homebrew/test/test_formula.rb b/Library/Homebrew/test/test_formula.rb
index 554a189fb0..bcd00a99b8 100644
--- a/Library/Homebrew/test/test_formula.rb
+++ b/Library/Homebrew/test/test_formula.rb
@@ -111,10 +111,6 @@ class FormulaTests < Test::Unit::TestCase
     assert_match /[0-9a-fA-F]{40}/, f.stable.checksum.hexdigest
     assert_match /[0-9a-fA-F]{64}/, f.devel.checksum.hexdigest
 
-    assert_nil f.stable.sha256
-    assert_nil f.bottle.sha256
-    assert_nil f.devel.sha1
-
     assert_equal 1, f.stable.mirrors.length
     assert f.bottle.mirrors.empty?
     assert_equal 1, f.devel.mirrors.length