1 files changed, 16 insertions, 2 deletions
diff --git a/class.c b/class.c
index 6f6c5d2b85..1c3391a5d4 100644
--- a/class.c
+++ b/class.c
@@ -19,7 +19,7 @@
 extern st_table *rb_class_tbl;
 
 VALUE
-rb_class_new(super)
+rb_class_boot(super)
     VALUE super;
 {
     NEWOBJ(klass, struct RClass);
@@ -33,6 +33,20 @@ rb_class_new(super)
     return (VALUE)klass;
 }
 
+VALUE
+rb_class_new(super)
+    VALUE super;
+{
+    Check_Type(super, T_CLASS);
+    if (super == rb_cClass) {
+	rb_raise(rb_eTypeError, "can't make subclass of Class");
+    }
+    if (FL_TEST(super, FL_SINGLETON)) {
+	rb_raise(rb_eTypeError, "can't make subclass of virtual class");
+    }
+    return rb_class_boot(super);
+}
+
 static int
 clone_method(mid, body, tbl)
     ID mid;
@@ -78,7 +92,7 @@ VALUE
 rb_singleton_class_new(super)
     VALUE super;
 {
-    VALUE klass = rb_class_new(super);
+    VALUE klass = rb_class_boot(super);
 
     FL_SET(klass, FL_SINGLETON);
     return klass;