2 files changed, 84 insertions, 29 deletions

diff --git a/src/class.c b/src/class.c
index f0393c7ec..6efc9f5e7 100644
--- a/src/class.c
+++ b/src/class.c
@@ -187,30 +187,39 @@ mrb_define_class(mrb_state *mrb, const char *name, struct RClass *super)
 struct RClass*
 mrb_vm_define_class(mrb_state *mrb, mrb_value outer, mrb_value super, mrb_sym id)
 {
-  struct RClass *c = 0;
+  struct RClass *c, *s;
 
   if (mrb_const_defined(mrb, outer, id)) {
     mrb_value v = mrb_const_get(mrb, outer, id);
 
+    mrb_check_type(mrb, v, MRB_TT_CLASS);
     c = mrb_class_ptr(v);
-    if (!mrb_nil_p(super) && (c->tt != MRB_TT_CLASS || c->super != mrb_class_ptr(super))) {
-      c = 0;
+    if (!mrb_nil_p(super)) {
+      if (mrb_type(super) != MRB_TT_CLASS) {
+        mrb_raise(mrb, E_TYPE_ERROR, "superclass must be a Class (%s given)", mrb_obj_classname(mrb, super));
+      }
+
+      if (!c->super || mrb_class_ptr(super) != mrb_class_real(c->super)) {
+        mrb_raise(mrb, E_TYPE_ERROR, "superclass mismatch for class %s", mrb_sym2name(mrb, id));
+      }
     }
+
+    return c;
   }
-  if (!c) {
-    struct RClass *s = 0;
 
-    if (!mrb_nil_p(super)) {
-      mrb_check_type(mrb, super, MRB_TT_CLASS);
-      s = mrb_class_ptr(super);
-    }
-    if (!s) {
-      s = mrb->object_class;
+  if (!mrb_nil_p(super)) {
+    if (mrb_type(super) != MRB_TT_CLASS) {
+      mrb_raise(mrb, E_TYPE_ERROR, "superclass must be a Class (%s given)", mrb_obj_classname(mrb, super));
     }
-    c = mrb_class_new(mrb, s);
-    setup_class(mrb, outer, c, id);
-    mrb_funcall(mrb, mrb_obj_value(s), "inherited", 1, mrb_obj_value(c));
+    s = mrb_class_ptr(super);
   }
+  else {
+    s = mrb->object_class;
+  }
+
+  c = mrb_class_new(mrb, s);
+  setup_class(mrb, outer, c, id);
+  mrb_funcall(mrb, mrb_obj_value(s), "inherited", 1, mrb_obj_value(c));
 
   return c;
 }
diff --git a/test/t/class.rb b/test/t/class.rb
index 1b809a832..d6c4715dd 100644
--- a/test/t/class.rb
+++ b/test/t/class.rb
@@ -47,36 +47,82 @@ end
 # Not ISO specified
 
 assert('Class 1') do
-  class C; end
-  C.class == Class
+  class C1; end
+  C1.class == Class
 end
 
 assert('Class 2') do
-  class C; end
-  C.new.class == C
+  class C2; end
+  C2.new.class == C2
 end
 
 assert('Class 3') do
-  class C; end
-  C.new.class.class == Class
+  class C3; end
+  C3.new.class.class == Class
 end
 
 assert('Class 4') do
-  class A; end
-  class C < A; end
-  C.class == Class
+  class C4_A; end
+  class C4 < C4_A; end
+  C4.class == Class
 end
 
 assert('Class 5') do
-  class A; end
-  class C < A; end
-  C.new.class == C
+  class C5_A; end
+  class C5 < C5_A; end
+  C5.new.class == C5
 end
 
 assert('Class 6') do
-  class A; end
-  class C < A; end
-  C.new.class.class == Class
+  class C6_A; end
+  class C6 < C6_A; end
+  C6.new.class.class == Class
+end
+
+assert('Class 7') do
+  class C7_A; end
+  class C7_B; end
+
+  class C7 < C7_A; end
+
+  error = false
+  begin
+    # Different superclass.
+    class C7 < C7_B; end
+  rescue TypeError
+    error = true
+  end
+
+  error
+end
+
+assert('Class 8') do
+  class C8_A; end
+
+  class C8; end  # superclass is Object
+
+  error = false
+  begin
+    # Different superclass.
+    class C8 < C8_A; end
+  rescue TypeError
+    error = true
+  end
+
+  error
+end
+
+assert('Class 9') do
+  Class9Const = "a"
+
+  error = false
+  begin
+    class Class9Const; end
+  rescue TypeError
+    error = true
+  end
+
+  error
 end
 
 assert('Class Module 1') do