diff --git a/moo/kernel/Boolean.moo b/moo/kernel/Boolean.moo
index 82f3d50..4e4ae8d 100644
--- a/moo/kernel/Boolean.moo
+++ b/moo/kernel/Boolean.moo
@@ -4,7 +4,7 @@ class Boolean(Object)
 	       and call subclassResponsibiltiy?" */
 }
 
-class True(Boolean)
+class(#final, #limited) True(Boolean)
 {
 	method not
 	{
@@ -47,7 +47,7 @@ class True(Boolean)
 	}
 }
 
-class False(Boolean)
+class(#final, #limited) False(Boolean)
 {
 	method not
 	{
diff --git a/moo/lib/gc.c b/moo/lib/gc.c
index d91ddcd..74283cb 100644
--- a/moo/lib/gc.c
+++ b/moo/lib/gc.c
@@ -320,7 +320,7 @@ static kernel_class_info_t kernel_classes[] =
 
 	{ 4,
 	  { 'T','r','u','e' },
-	  0,
+	  MOO_CLASS_SELFSPEC_FLAG_LIMITED | MOO_CLASS_SELFSPEC_FLAG_FINAL,
 	  0,
 	  0,
 	  0,
@@ -329,7 +329,7 @@ static kernel_class_info_t kernel_classes[] =
 
 	{ 5,
 	  { 'F','a','l','s','e' },
-	  0,
+	  MOO_CLASS_SELFSPEC_FLAG_LIMITED | MOO_CLASS_SELFSPEC_FLAG_FINAL,
 	  0,
 	  0,
 	  0,