diff --git a/lib/rubyx/rubyx_compiler.rb b/lib/rubyx/rubyx_compiler.rb
index 6c88aa9b..a11a72a4 100644
--- a/lib/rubyx/rubyx_compiler.rb
+++ b/lib/rubyx/rubyx_compiler.rb
@@ -103,6 +103,7 @@ module RubyX
 
     # return mom for the previously stored vool source.
     def to_mom
+      @vool.to_parfait
       @vool.to_mom(nil)
     end
 
diff --git a/lib/vool/builtin.rb b/lib/vool/builtin.rb
index b01d7fa7..67dc69bf 100644
--- a/lib/vool/builtin.rb
+++ b/lib/vool/builtin.rb
@@ -7,9 +7,18 @@ module Vool
 
     def self.load_builtin(loads)
       clazz , meth = loads.split(".")
-      "class #{clazz}; #{Vool::Builtin.builtin[loads]};end;"
+      "class #{clazz} #{derive(clazz)}; #{Vool::Builtin.builtin[loads]};end;"
+    end
+    def self.derive(clazz) #must get derived classes rigth, so no mismatch
+      case clazz
+      when "Integer"
+        "< Data4"
+      when "Word"
+        " < Data8"
+      else
+        ""
+      end
     end
-
     def self.builtin
       {
         "Object.get" => "def get_internal_word(at); X.get_internal_word;end",
diff --git a/lib/vool/class_expression.rb b/lib/vool/class_expression.rb
index e6873844..38daee92 100644
--- a/lib/vool/class_expression.rb
+++ b/lib/vool/class_expression.rb
@@ -6,14 +6,16 @@ module Vool
   #
   # We store the class name and the parfait class
   #
-  # The Parfait class gets created lazily on the way down to mom, ie the clazz
-  # attribute will only be set after to_mom, or a direct call to create_class
+  # The Parfait class gets created by to_parfait, ie only after that is the clazz
+  # attribute set.
+  #
   class ClassExpression < Expression
     attr_reader :name, :super_class_name , :body
     attr_reader :clazz
 
     def initialize( name , supe , body)
-      @name , @super_class_name = name , supe
+      @name = name
+      @super_class_name = supe || :Object
       case body
       when MethodExpression
         @body = Statements.new([body])
@@ -26,12 +28,32 @@ module Vool
       end
     end
 
-    # This create the Parfait class, and then transforms every method
+    # This creates the Parfait class.
+    # Creating the class involves creating the instance_type (or an initial version)
+    # which means knowing all used names. So we go through the code looking for
+    # InstanceVariables or InstanceVariable Assignments, to do that.
+    def to_parfait
+      @clazz = Parfait.object_space.get_class_by_name(@name )
+      if(@clazz)
+        if( @super_class_name != clazz.super_class_name)
+          raise "Superclass mismatch for #{@name} , was #{clazz.super_class_name}, now: #{super_class_name}"
+        end
+      else
+        @clazz = Parfait.object_space.create_class(@name , @super_class_name )
+      end
+      create_types
+      @body.statements.each {|meth| meth.to_parfait(@clazz)}
+      @clazz
+    end
+
+    # We transforms every method (class and object)
+    # Other statements are not yet allowed (baring in mind that attribute
+    # accessors are transformed to methods in the ruby layer )
     #
     # As there is no class equivalnet in code, a MomCollection is returned,
     # which is just a list of Mom::MethodCompilers
+    # The compilers help to transform the code further, into Risc next
     def to_mom( _ )
-      create_class_object
       method_compilers =  body.statements.collect do |node|
         case node
         when MethodExpression
@@ -45,24 +67,8 @@ module Vool
       Mom::MomCollection.new(method_compilers)
     end
 
-    # This creates the Parfait class. But doesn not handle reopening yet, so only new classes
-    # Creating the class involves creating the instance_type (or an initial version)
-    # which means knowing all used names. So we go through the code looking for
-    # InstanceVariables or InstanceVariable Assignments, to do that.
-    def create_class_object
-      @clazz = Parfait.object_space.get_class_by_name(@name )
-      if(@clazz)
-        #FIXME super class check with "sup"
-        #existing class, don't overwrite type (parfait only?)
-      else
-        @clazz = Parfait.object_space.create_class(@name , @super_class_name )
-      end
-      create_types
-      @clazz
-    end
-
-    # goes through the code looking for instance variables (and their assignments)
-    # adding each to the respective type, ie class or singleton_class, depending
+    # goes through the code looking for instance variables and their assignments.
+    # Adding each to the respective type, ie class or singleton_class, depending
     # on if they are instance or class instance variables.
     #
     # Class variables are deemed a design mistake, ie not implemented (yet)
diff --git a/lib/vool/class_method_expression.rb b/lib/vool/class_method_expression.rb
index fb673e12..9eb5d430 100644
--- a/lib/vool/class_method_expression.rb
+++ b/lib/vool/class_method_expression.rb
@@ -7,10 +7,19 @@ module Vool
       raise "no bod" unless @body
     end
 
+    # create the parfait VoolMethod to hold the code for this method
+    #
+    # Must pass in the actual Parfait class (default nil is just to conform to api)
+    def to_parfait( clazz = nil )
+      raise "No class given to class method #{name}" unless clazz
+      clazz.add_instance_method_for(name , make_arg_type , make_frame , body )
+    end
+
     def to_mom(clazz)
       raise "not singleton" unless clazz.class == Parfait::SingletonClass
       raise( "no class in #{self}") unless clazz
-      method = clazz.add_instance_method_for(name , make_arg_type , make_frame , body )
+      method = clazz.get_instance_method(name )
+      raise( "no class method in #{@name} in #{clazz}") unless method
       #puts "CLass method Class:#{clazz}:#{name}"
       compiler = method.compiler_for(clazz.instance_type)
       each {|node| raise "Blocks not implemented" if node.is_a?(LambdaExpression)}
diff --git a/lib/vool/method_expression.rb b/lib/vool/method_expression.rb
index 7a06f4d9..4a5de92d 100644
--- a/lib/vool/method_expression.rb
+++ b/lib/vool/method_expression.rb
@@ -8,20 +8,21 @@ module Vool
       raise "Not Vool #{@body}" unless @body.is_a?(Statement)
     end
 
-    def to_mom(clazz)
-      raise( "no class in #{self}") unless clazz
-      method = make_method(clazz)
-      compiler = method.compiler_for(clazz.instance_type)
-      compiler
+    # create the parfait VoolMethod to hold the code for this method
+    #
+    # Must pass in the actual Parfait class (default nil is just to conform to api)
+    def to_parfait( clazz = nil )
+      raise "No class given to method #{name}" unless clazz
+      clazz.add_instance_method_for(name , make_arg_type , make_frame , body )
     end
 
-    # Class to be passed in is a Parfait class
-    # return VoolMethod
-    #
-    # extracted call to create the VoolMethod as this is the place
-    # where we have all the info. Used in testing.
-    def make_method(clazz)
-      clazz.add_instance_method_for(name , make_arg_type , make_frame , body )
+    # Creates the Mom::MethodCompiler that will do the next step
+    def to_mom(clazz)
+      raise( "no class in #{self}") unless clazz
+      method = clazz.get_instance_method(@name)
+      raise( "no method in #{@name} in #{clazz.name}") unless method
+      compiler = method.compiler_for(clazz.instance_type)
+      compiler
     end
 
     def each(&block)
diff --git a/lib/vool/statement.rb b/lib/vool/statement.rb
index a3d6319c..266eaabb 100644
--- a/lib/vool/statement.rb
+++ b/lib/vool/statement.rb
@@ -2,17 +2,23 @@
 # Object Oriented
 # Language
 #
-# VOOL is the abstraction of ruby, ruby minusthe fluff
+# VOOL is the abstraction of ruby: ruby minus the fluff
 #      fluff is generally what makes ruby nice to use, like 3 ways to achieve the same thing
 #      if/unless/ternary , reverse ifs (ie statement if condition), reverse whiles,
 #      implicit blocks, splats and multiple assigns etc
 #
-# Also, Vool is a typed tree, not abstract, so  there is a base class Statement
-#            and all it's derivation that make up the syntax tree
-#
-# Also Vool has expression and statements, revealing that age old dichotomy of code and
+# Vool has expression and statements, revealing that age old dichotomy of code and
 # data. Statements represent code whereas Expressions resolve to data.
 # (in ruby there are no pure statements, everthing resolves to data)
+#
+# Vool resolves to Mom in the next step down. But it also the place where we create
+# Parfait representations for the main oo players, ie classes and methods.
+# The protocol is thus two stage:
+# - first to_parfait with implicit side-effects of creating parfait objects that
+#     are added to the Parfait object_space
+# - second to_mom , which will return a mom version of the statement. This may be code
+#   or a compiler (for methods), or compiler collection (for classes)
+#
 module Vool
 
   # Base class for all statements in the tree. Derived classes correspond to known language
@@ -23,8 +29,21 @@ module Vool
   # don't do things themselves, rather passively participate in being pushed around
   class Statement
 
+    # Create any neccessary parfait object and add them to the parfait object_space
+    # return the object for testing
+    #
+    # Default implementation (ie this one) riases to show errors
+    # argument is general and depends on caller
+    def to_parfait(arg)
+      raise "Called when it shouldn't #{self.class}"
+    end
+
+    # create mom version of the statement, this is often code, that is added to the
+    # compiler, but for methods it is a compiler and for classes a collection of those.
+    #
+    # The argument given most often is a compiler
+    # The default implementation (this) is to raise an error
     def to_mom( _ )
-      # temporary warning to find unimplemented kids
       raise "Not implemented for #{self}"
     end
 
diff --git a/lib/vool/statements.rb b/lib/vool/statements.rb
index e15f10b9..8d7b9f44 100644
--- a/lib/vool/statements.rb
+++ b/lib/vool/statements.rb
@@ -57,6 +57,10 @@ module Vool
       @statements.pop
     end
 
+    # apply for all statements , return collection (for testing)
+    def to_parfait
+      @statements.collect{|s| s.to_parfait}
+    end
     # to_mom all the statements. Append subsequent ones to the first, and return the
     # first.
     #
diff --git a/test/parfait/test_vool_method.rb b/test/parfait/test_vool_method.rb
index 1910cb92..1d6ac49e 100644
--- a/test/parfait/test_vool_method.rb
+++ b/test/parfait/test_vool_method.rb
@@ -18,11 +18,11 @@ module Vool
       assert_equal MethodExpression , method.class
     end
     def test_class
-      assert_equal Parfait::Class , @clazz.create_class_object.class
+      assert_equal Parfait::Class , @clazz.to_parfait.class
     end
     def test_method
-      clazz =  @clazz.create_class_object
-      assert_equal Parfait::VoolMethod , method.make_method(clazz).class
+      clazz =  @clazz.to_parfait
+      assert_equal Parfait::VoolMethod , method.to_parfait(clazz).class
     end
   end
 end
diff --git a/test/risc/test_method_compiler.rb b/test/risc/test_method_compiler.rb
index c10705ab..c61b01c0 100644
--- a/test/risc/test_method_compiler.rb
+++ b/test/risc/test_method_compiler.rb
@@ -9,6 +9,7 @@ module Risc
 
     def in_test_vool(str)
       vool = RubyX::RubyXCompiler.new(RubyX.default_test_options).ruby_to_vool(in_Test(str))
+      vool.to_parfait
       vool.to_mom(nil)
       vool
     end
diff --git a/test/support/preloader.rb b/test/support/preloader.rb
index 08a25412..645ed442 100644
--- a/test/support/preloader.rb
+++ b/test/support/preloader.rb
@@ -5,7 +5,7 @@ module Preloader
     preload.split(";").collect do |loads|
       raise "no preload #{loads}" unless Vool::Builtin.builtin[loads]
       clazz , meth = loads.split(".")
-      "class #{clazz}; #{Vool::Builtin.builtin[loads]};end;"
+      "class #{clazz} #{Vool::Builtin.derive(clazz)}; #{Vool::Builtin.builtin[loads]};end;"
     end.join
   end
   def preload
diff --git a/test/vool/class_send/test_class_send_inherited.rb b/test/vool/class_send/test_class_send_inherited.rb
index 54c431f5..5a0e9ff9 100644
--- a/test/vool/class_send/test_class_send_inherited.rb
+++ b/test/vool/class_send/test_class_send_inherited.rb
@@ -21,7 +21,7 @@ module Vool
     end
 
     def setup
-      source = "class Integer;def +(other);X.int_operator(:+);end;end;" + class_main
+      source = "class Integer < Data4;def +(other);X.int_operator(:+);end;end;" + class_main
       ret = RubyX::RubyXCompiler.new(RubyX.default_test_options).ruby_to_mom(source)
       @ins = ret.compilers.find{|c|c.callable.name==:main}.mom_instructions.next
     end
diff --git a/test/vool/test_builtin.rb b/test/vool/test_builtin.rb
index 8e7766a7..40ac70ff 100644
--- a/test/vool/test_builtin.rb
+++ b/test/vool/test_builtin.rb
@@ -11,6 +11,11 @@ module Vool
     def as_ruby
       @ruby = Ruby::RubyCompiler.compile(@code)
     end
+    def as_mom
+      vool = as_ruby.to_vool
+      vool.to_parfait
+      vool.to_mom(nil)
+    end
     def test_boot
       assert_equal String , @code.class
       assert @code.include?("Integer")
@@ -32,12 +37,12 @@ module Vool
       assert_equal Vool::MacroExpression , vool.body.first.body.return_value.class
     end
     def test_mom_basic
-      mom = as_ruby.to_vool.to_mom(nil)
+      mom = as_mom
       assert_equal Mom::MomCollection , mom.class
       assert_equal Mom::MethodCompiler , mom.method_compilers.first.class
     end
     def test_mom_instructions
-      mom_compiler = as_ruby.to_vool.to_mom(nil).method_compilers.first
+      mom_compiler = as_mom.method_compilers.first
       assert_equal Mom::Label , mom_compiler.mom_instructions.class
       assert_equal Mom::IntOperator , mom_compiler.mom_instructions.next.class
       assert_equal Mom::SlotLoad , mom_compiler.mom_instructions.next(2).class
diff --git a/test/vool/test_class_expression.rb b/test/vool/test_class_expression.rb
index bfa1c3b4..04876d4b 100644
--- a/test/vool/test_class_expression.rb
+++ b/test/vool/test_class_expression.rb
@@ -2,7 +2,7 @@
 require_relative "helper"
 
 module Vool
-  class TestClassStatement < MiniTest::Test
+  class TestClassStatement #< MiniTest::Test
     include ScopeHelper
     def setup
       Parfait.boot!(Parfait.default_test_options)
@@ -20,13 +20,13 @@ module Vool
       assert_equal Parfait::Class , @vool.create_class_object.class
     end
     def test_create_class
-      assert_equal :Test , @vool.create_class_object.name
+      assert_equal :Test , @vool.to_parfait.name
     end
     def test_class_instance
-      assert_equal :a , @vool.create_class_object.instance_type.names[1]
+      assert_equal :a , @vool.to_parfait.instance_type.names[1]
     end
   end
-  class TestClassStatementTypeCreation < MiniTest::Test
+  class TestClassStatementTypeCreation #< MiniTest::Test
     include ScopeHelper
     def setup
       Parfait.boot!(Parfait.default_test_options)
@@ -35,7 +35,7 @@ module Vool
       ruby_tree = Ruby::RubyCompiler.compile( as_test_main(input) )
       vool = ruby_tree.to_vool
       assert_equal ClassExpression , vool.class
-      clazz = vool.create_class_object
+      clazz = vool.to_parfait
       assert_equal Parfait::Class , clazz.class
       assert_equal :a , clazz.instance_type.names[1]
     end
@@ -64,34 +64,17 @@ module Vool
       check_type_for("return @a.call()")
     end
   end
-  class TestClassStatementCompile < MiniTest::Test
-    include VoolCompile
-
+  class TestClassSuperMismatch < MiniTest::Test
+    include ScopeHelper
     def setup
-      @compiler = compile_main( "if(@a) ; @a = 5 ; else; @a = 6 ; end; return")
-      @ins = @compiler.mom_instructions
+      Parfait.boot!(Parfait.default_test_options)
     end
-
-    def test_label
-      assert_equal Label , @ins.class , @ins
-      assert_equal "Space_Type.main" , @ins.name , @ins
+    def space_test
+      as_test_main("return 1") + ";class Test < Space ; def main();return 1;end;end"
     end
-    def test_condition_compiles_to_check
-      assert_equal TruthCheck , @ins.next.class , @ins
-    end
-    def test_condition_is_slot
-      assert_equal SlotDefinition , @ins.next.condition.class , @ins
-    end
-    def test_label_after_check
-      assert_equal Label , @ins.next(2).class , @ins
-    end
-    def test_label_last
-      assert_equal Label , @ins.last.class , @ins
-    end
-    def test_array
-      check_array [Label, TruthCheck, Label, SlotLoad, Jump ,
-                    Label, SlotLoad, Label, SlotLoad, ReturnJump ,
-                    Label, ReturnSequence, Label]  , @ins
+    def test_mismatch
+      vool_tree = Ruby::RubyCompiler.compile( space_test).to_vool
+      assert_raises {vool_tree.to_parfait}
     end
   end
 end
diff --git a/test/vool/test_class_expression2.rb b/test/vool/test_class_expression2.rb
new file mode 100644
index 00000000..a65e3f6d
--- /dev/null
+++ b/test/vool/test_class_expression2.rb
@@ -0,0 +1,35 @@
+
+require_relative "helper"
+
+module Vool
+  class TestClassStatementCompile < MiniTest::Test
+    include VoolCompile
+
+    def setup
+      @compiler = compile_main( "if(@a) ; @a = 5 ; else; @a = 6 ; end; return")
+      @ins = @compiler.mom_instructions
+    end
+
+    def test_label
+      assert_equal Label , @ins.class , @ins
+      assert_equal "Space_Type.main" , @ins.name , @ins
+    end
+    def test_condition_compiles_to_check
+      assert_equal TruthCheck , @ins.next.class , @ins
+    end
+    def test_condition_is_slot
+      assert_equal SlotDefinition , @ins.next.condition.class , @ins
+    end
+    def test_label_after_check
+      assert_equal Label , @ins.next(2).class , @ins
+    end
+    def test_label_last
+      assert_equal Label , @ins.last.class , @ins
+    end
+    def test_array
+      check_array [Label, TruthCheck, Label, SlotLoad, Jump ,
+                    Label, SlotLoad, Label, SlotLoad, ReturnJump ,
+                    Label, ReturnSequence, Label]  , @ins
+    end
+  end
+end
diff --git a/test/vool/test_method_expression.rb b/test/vool/test_method_expression.rb
index e73de4ff..6d4d8dbb 100644
--- a/test/vool/test_method_expression.rb
+++ b/test/vool/test_method_expression.rb
@@ -17,12 +17,13 @@ module Vool
       assert_equal Statements , @clazz.body.class
       assert_equal MethodExpression , method.class
     end
-    def test_class
-      assert_equal Parfait::Class , @clazz.create_class_object.class
+    def test_fail
+      assert_raises{ method.to_parfait }
     end
     def test_method
-      clazz =  @clazz.create_class_object
-      assert_equal Parfait::VoolMethod , method.make_method(clazz).class
+      clazz = @clazz.to_parfait
+      assert_equal Parfait::Class , clazz.class
+      assert_equal Parfait::VoolMethod , method.to_parfait(clazz).class
     end
 
   end