diff --git a/lib/mom/instruction/message_setup.rb b/lib/mom/instruction/message_setup.rb
index a53c1e21..7632147d 100644
--- a/lib/mom/instruction/message_setup.rb
+++ b/lib/mom/instruction/message_setup.rb
@@ -36,16 +36,16 @@ module Mom
     def build_with(builder)
       case from = method_source
       when Parfait::CallableMethod
-        builder.build { callable << from }
+        builder.build { callable! << from }
       when Parfait::CacheEntry
         builder.build do
-          cache_entry << from
-          callable << cache_entry[:cached_method]
+          cache_entry! << from
+          callable! << cache_entry[:cached_method]
         end
       when Integer
         builder.build do
-          arguments << message[:arguments]
-          callable << arguments[ from ]
+          arguments! << message[:arguments]
+          callable! << arguments[ from ]
         end
       else
         raise "unknown source #{method_source.class}:#{method_source}"
@@ -64,11 +64,11 @@ module Mom
     # set the method into the message
     def build_message_data( builder )
       builder.build do
-        space << Parfait.object_space
-        next_message << space[:next_message]
+        space! << Parfait.object_space
+        next_message! << space[:next_message]
 
         #FIXME in a multithreaded future this should be done using lock free compare and swap.
-        next_message_reg << next_message[:next_message]
+        next_message_reg! << next_message[:next_message]
         space[:next_message] << next_message_reg
 
         message[:next_message] << next_message
diff --git a/lib/mom/instruction/resolve_method.rb b/lib/mom/instruction/resolve_method.rb
index df008c4e..6c69ed77 100644
--- a/lib/mom/instruction/resolve_method.rb
+++ b/lib/mom/instruction/resolve_method.rb
@@ -37,20 +37,20 @@ module Mom
       cache_entry_ = @cache_entry
       builder = compiler.code_builder(self)
       builder.build do
-        word << name_
-        cache_entry << cache_entry_
+        word! << name_
+        cache_entry! << cache_entry_
 
-        type << cache_entry[:cached_type]
-        callable_method << type[:methods]
+        type! << cache_entry[:cached_type]
+        callable_method! << type[:methods]
 
         add_code while_start_label
 
-        space << Parfait.object_space
+        space! << Parfait.object_space
         space << space[:nil_object]
         space - callable_method
         if_zero exit_label
 
-        name << callable_method[:name]
+        name! << callable_method[:name]
         name - word
 
         if_zero ok_label
diff --git a/lib/mom/instruction/return_sequence.rb b/lib/mom/instruction/return_sequence.rb
index 0da0dce5..08d2c492 100644
--- a/lib/mom/instruction/return_sequence.rb
+++ b/lib/mom/instruction/return_sequence.rb
@@ -23,17 +23,17 @@ module Mom
       compiler.reset_regs
       builder = compiler.code_builder(self)
       builder.build do
-        object << message[:return_value]
-        caller_reg << message[:caller]
+        object! << message[:return_value]
+        caller_reg! << message[:caller]
         caller_reg[:return_value] << object
-        space << Parfait.object_space
-        next_message << space[:next_message]
+        space! << Parfait.object_space
+        next_message! << space[:next_message]
         message[:next_message] << next_message
         space[:next_message] << message
       end
       compiler.reset_regs
       builder.build do
-        return_address << message[:return_address]
+        return_address! << message[:return_address]
         return_address << return_address[ Parfait::Integer.integer_index]
         message << message[:caller]
         return_address.function_return
diff --git a/lib/risc/builder.rb b/lib/risc/builder.rb
index a4c7c798..a66890c0 100644
--- a/lib/risc/builder.rb
+++ b/lib/risc/builder.rb
@@ -28,17 +28,21 @@ module Risc
     # make the magic: convert incoming names into registers that have the
     # type set according to the name (using resolve_type)
     # anmes are stored, so subsequent calls use the same register
-    def method_missing(*args)
-      super if args.length != 1
-      name = args[0]
+    def method_missing(name , *args)
+      super if args.length != 0
+      name = name.to_s
       return @names[name] if @names.has_key?(name)
-      if name == :message
+      if name == "message"
         reg = Risc.message_reg
         reg.builder = self
-      elsif name.to_s.index("label")
+        return reg
+      end
+      if name.index("label")
         reg = Risc.label( @source , "#{name}_#{object_id}")
         @source_used = true
       else
+        raise "Must create (with !) before using #{name}" unless name[-1] == "!"
+        name = name[0 ... -1]
         type = infer_type(name )
         reg = @compiler.use_reg( type.object_class.name )
         reg.builder = self
@@ -90,6 +94,7 @@ module Risc
     # but since the names in the builder are not variables, we need this method
     # as it says, swap the two names around. Names must exist
     def swap_names(left , right)
+      left , right = left.to_s , right.to_s
       l = @names[left]
       r = @names[right]
       raise "No such name #{left}" unless l
@@ -127,9 +132,9 @@ module Risc
       to.builder = self    # esecially div10 comes in without having used builder
       from.builder = self  # not named regs, different regs ==> silent errors
       build do
-        space << Parfait.object_space
+        space! << Parfait.object_space
         to << space[:next_integer]
-        integer_tmp << to[:next_integer]
+        integer_tmp! << to[:next_integer]
         space[:next_integer] << integer_tmp
         to[Parfait::Integer.integer_index] << from
       end
diff --git a/lib/risc/builtin/integer.rb b/lib/risc/builtin/integer.rb
index 4239ee2f..75d851dc 100644
--- a/lib/risc/builtin/integer.rb
+++ b/lib/risc/builtin/integer.rb
@@ -14,9 +14,9 @@ module Risc
         def div4(context)
           compiler = compiler_for(:Integer,:div4 ,{})
           compiler.compiler_builder(compiler.source).build do
-            integer << message[:receiver]
+            integer! << message[:receiver]
             integer.reduce_int
-            integer_reg << 2
+            integer_reg! << 2
             integer.op :>> , integer_reg
             add_new_int("div4", integer , integer_reg)
             message[:return_value] << integer_reg
@@ -52,8 +52,8 @@ module Risc
           compiler = compiler_for(:Integer, operator ,{other: :Integer})
           builder = compiler.compiler_builder(compiler.source)
           builder.build do
-            integer << message[:receiver]
-            integer_reg << message[:arguments]
+            integer! << message[:receiver]
+            integer_reg! << message[:arguments]
             integer_reg << integer_reg[ 1]
             integer.reduce_int
             integer_reg.reduce_int
@@ -61,7 +61,7 @@ module Risc
             integer.op :- , integer_reg
             if_minus false_label
             if_zero( false_label ) if operator.to_s.length == 1
-            object << Parfait.object_space.true_object
+            object! << Parfait.object_space.true_object
             branch merge_label
             add_code false_label
             object << Parfait.object_space.false_object
@@ -89,8 +89,8 @@ module Risc
           compiler = compiler_for(:Integer, op_sym ,{other: :Integer})
           builder = compiler.compiler_builder(compiler.source)
           builder.build do
-            integer << message[:receiver]
-            integer_reg << message[:arguments]
+            integer! << message[:receiver]
+            integer_reg! << message[:arguments]
             integer_reg << integer_reg[ 1]
             integer.reduce_int
             integer_reg.reduce_int
diff --git a/lib/risc/builtin/object.rb b/lib/risc/builtin/object.rb
index 5bfc1f9e..016db9d0 100644
--- a/lib/risc/builtin/object.rb
+++ b/lib/risc/builtin/object.rb
@@ -9,9 +9,9 @@ module Risc
         def get_internal_word( context )
           compiler = compiler_for(:Object , :get_internal_word ,{at: :Integer})
           compiler.compiler_builder(compiler.source).build do
-            object << message[:receiver]
-            integer << message[:arguments]
-            integer << integer_reg[1]
+            object! << message[:receiver]
+            integer! << message[:arguments]
+            integer << integer[1]
             integer.reduce_int
             object << object[integer]
             message[:return_value] << object
@@ -25,10 +25,10 @@ module Risc
         def set_internal_word( context )
           compiler = compiler_for(:Object , :set_internal_word , {at: :Integer, :value => :Object} )
           compiler.compiler_builder(compiler.source).build do
-            object << message[:receiver]
-            integer << message[:arguments]
-            object_reg << integer[ 2]
-            integer << integer[ 1]
+            object! << message[:receiver]
+            integer! << message[:arguments]
+            object_reg! << integer[ 2]
+            integer << integer[1]
             integer.reduce_int
             object[integer] << object_reg
             message[:return_value] << object_reg
@@ -56,9 +56,9 @@ module Risc
                             Parfait::NamedList.type_for({}) , Parfait::NamedList.type_for({}))
           builder = compiler.compiler_builder(compiler.source)
           builder.build do
-            space << Parfait.object_space
+            space! << Parfait.object_space
             message << space[:next_message]
-            next_message << message[:next_message]
+            next_message! << message[:next_message]
             space[:next_message] << next_message
           end
 
@@ -128,7 +128,7 @@ module Risc
           r8 = RegisterValue.new( :r8 , :Message)
           int = builder.compiler.use_reg(:Integer)
           builder.build do
-            integer_reg << message
+            integer_reg! << message
             message << r8
             add_new_int( "_restore_message", integer_reg , int )
             message[:return_value] << int
diff --git a/lib/risc/builtin/word.rb b/lib/risc/builtin/word.rb
index fa55c778..090eebd6 100644
--- a/lib/risc/builtin/word.rb
+++ b/lib/risc/builtin/word.rb
@@ -28,8 +28,8 @@ module Risc
         def get_internal_byte( context)
           compiler = compiler_for(:Word , :get_internal_byte , {at: :Integer})
           compiler.compiler_builder(compiler.source).build do
-            object << message[:receiver]
-            integer << message[:arguments]
+            object! << message[:receiver]
+            integer! << message[:arguments]
             integer << integer[1]
             integer.reduce_int
             object <= object[integer]
@@ -46,11 +46,11 @@ module Risc
         def set_internal_byte( context )
           compiler = compiler_for(:Word, :set_internal_byte , {at: :Integer , :value => :Integer} )
           compiler.compiler_builder(compiler.source).build do
-            word << message[:receiver]
-            integer << message[:arguments]
+            word! << message[:receiver]
+            integer! << message[:arguments]
             integer << integer[1]
-            integer_reg << message[:arguments]
-            integer_obj << integer_reg[2]
+            integer_reg! << message[:arguments]
+            integer_obj! << integer_reg[2]
             integer_reg << integer_reg[2]
             integer.reduce_int
             integer_reg.reduce_int
diff --git a/test/risc/test_builder.rb b/test/risc/test_builder.rb
index adc35735..03120f8c 100644
--- a/test/risc/test_builder.rb
+++ b/test/risc/test_builder.rb
@@ -17,12 +17,15 @@ module Risc
       assert_nil @builder.built
     end
     def test_alloc_space
-      reg = @builder.space
+      reg = @builder.space!
       assert_equal RegisterValue , reg.class
       assert_equal :Space , reg.type.class_name
     end
+    def test_not_alloc_space
+      assert_raises {@builder.space}
+    end
     def test_next_message
-      reg = @builder.next_message
+      reg = @builder.next_message!
       assert_equal :r1 , reg.symbol
       assert_equal :Message , reg.type.class_name
     end
@@ -33,31 +36,31 @@ module Risc
     end
     def test_returns_built
       r1 = RegisterValue.new(:r1 , :Space)
-      built = @builder.build{ space << r1 }
+      built = @builder.build{ space! << r1 }
       assert_equal Transfer , built.class
     end
     def test_returns_two
       r1 = RegisterValue.new(:r1 , :Space)
-      built = @builder.build{ space << r1 ; space << r1}
+      built = @builder.build{ space! << r1 ; space << r1}
       assert_equal Transfer , built.next.class
     end
     def test_returns_slot
       r2 = RegisterValue.new(:r2 , :Message)
       r2.builder = @builder
-      built = @builder.build{ r2 << space[:next_message] }
+      built = @builder.build{ r2 << space![:next_message] }
       assert_equal SlotToReg , built.class
       assert_equal :r1 , built.array.symbol
     end
     def test_returns_slot_reverse
       r2 = RegisterValue.new(:r2 , :Message)
       r2.builder = @builder
-      built = @builder.build{ r2 << space[:next_message] }
+      built = @builder.build{ r2 << space![:next_message] }
       assert_equal SlotToReg , built.class
       assert_equal :r1 , built.array.symbol
     end
     def test_reuses_names
       r1 = RegisterValue.new(:r1 , :Space)
-      built = @builder.build{ space << r1 ; space << r1}
+      built = @builder.build{ space! << r1 ; space << r1}
       assert_equal built.to.symbol , built.next.to.symbol
     end
     def test_uses_message_as_message
@@ -92,7 +95,7 @@ module Risc
       assert_equal @label , ret.label
     end
     def test_minus
-      op = @builder.build {space - callable_method}
+      op = @builder.build {space! - callable_method!}
       assert_equal OperatorInstruction , op.class
       assert_equal :- , op.operator
       assert_equal :Space , op.left.type.class_name
diff --git a/test/risc/test_builder1.rb b/test/risc/test_builder1.rb
index 6362e5c5..bd79df69 100644
--- a/test/risc/test_builder1.rb
+++ b/test/risc/test_builder1.rb
@@ -12,17 +12,17 @@ module Risc
     end
     def test_inserts_built
       r1 = RegisterValue.new(:r1 , :Space)
-      @builder.build{ space << r1 }
+      @builder.build{ space! << r1 }
       assert_equal Transfer , @compiler.risc_instructions.next.class
       assert_equal RegisterValue ,  @builder.space.class
     end
     def test_loads
-      @builder.build{ space << Parfait.object_space }
+      @builder.build{ space! << Parfait.object_space }
       assert_equal LoadConstant , @compiler.risc_instructions.next.class
       assert_equal RegisterValue ,  @builder.space.class
     end
     def test_two
-      @builder.build{ space << Parfait.object_space ; integer << 1}
+      @builder.build{ space! << Parfait.object_space ; integer! << 1}
       assert_equal LoadConstant , @compiler.risc_instructions.next.class
       assert_equal LoadData , @compiler.risc_instructions.next(2).class
     end