diff --git a/lib/mom/instruction/dynamic_call.rb b/lib/mom/instruction/dynamic_call.rb
index 52e1a5d1..ed036cc6 100644
--- a/lib/mom/instruction/dynamic_call.rb
+++ b/lib/mom/instruction/dynamic_call.rb
@@ -12,12 +12,10 @@ module Mom
   # See vool send statement
   #
   class DynamicCall < Instruction
-    attr :cached_type
-    attr :cached_method
+    attr :cache_entry
 
     def initialize(type = nil, method = nil)
-      @cached_type = type
-      @cached_method = method
+      @cache_entry = Parfait::CacheEntry.new(type, method)
     end
 
     def to_risc(context)
diff --git a/lib/parfait.rb b/lib/parfait.rb
index 894b75ba..16ce1375 100644
--- a/lib/parfait.rb
+++ b/lib/parfait.rb
@@ -13,6 +13,7 @@ require_relative "parfait/typed_method"
 require_relative "parfait/vool_method"
 require_relative "parfait/dictionary"
 require_relative "parfait/type"
+require_relative "parfait/cache_entry"
 require_relative "parfait/message"
 require_relative "parfait/named_list"
 require_relative "parfait/space"
diff --git a/lib/parfait/cache_entry.rb b/lib/parfait/cache_entry.rb
new file mode 100644
index 00000000..5ba88d5b
--- /dev/null
+++ b/lib/parfait/cache_entry.rb
@@ -0,0 +1,17 @@
+# For dynamic calls (ie method calls where the method can not be determined at compile time)
+# we resolve the method at runtime, and then cache it. Aaron has shown that over 99%
+# of call sites are type stable, so one cache entry at the moment
+#
+# A cache entry stores the type of the object and the TypedMethod that is to be called
+# This is used in DynamicCall, see there
+#
+module Parfait
+  class CacheEntry < Object
+    attr :cached_type
+    attr :cached_method
+    def initialize(type , method)
+      @cached_type = type
+      @cached_method = method
+    end
+  end
+end
diff --git a/lib/risc/boot.rb b/lib/risc/boot.rb
index 148f0f4e..138efd0a 100644
--- a/lib/risc/boot.rb
+++ b/lib/risc/boot.rb
@@ -139,6 +139,7 @@ module Risc
           :Class => {:instance_methods => :List, :instance_type => :Type, :name => :Word,
                       :super_class_name => :Word , :instance_names => :List },
           :Dictionary => {:keys => :List , :values => :List  } ,
+          :CacheEntry => {:cached_type => :Type , :cached_method => :TypedMethod  } ,
           :TypedMethod => {:name => :Word, :source => :Object, :instructions => :Object, :binary => :Object,
                       :arguments => :Type , :for_type => :Type, :frame => :Type } ,
         }