try.diff

diff --git a/insns.def b/insns.def
index 81aca8f..1c14bb9 100644
--- a/insns.def
+++ b/insns.def
@@ -318,8 +318,15 @@ putspecialobject
 	val = rb_mRubyVMFrozenCore;
 	break;
       case VM_SPECIAL_OBJECT_CBASE:
-	val = vm_get_cbase(GET_ISEQ(), GET_EP());
+      {
+	rb_control_frame_t *class_cfp = find_magic_class(th->cfp);
+	if (class_cfp) {
+	  val = class_cfp->cklass;
+	} else {
+	  val = vm_get_cbase(GET_ISEQ(), GET_EP());
+	}
 	break;
+      }
       case VM_SPECIAL_OBJECT_CONST_BASE:
 	val = vm_get_const_base(GET_ISEQ(), GET_EP());
 	break;
@@ -914,6 +921,7 @@ defineclass
 (VALUE val)
 {
     VALUE klass;
+    rb_control_frame_t *cft;
     rb_vm_defineclass_type_t type = VM_DEFINECLASS_TYPE(flags);
 
     switch (type) {
@@ -994,10 +1002,12 @@ defineclass
     COPY_CREF(class_iseq->cref_stack, vm_cref_push(th, klass, NOEX_PUBLIC, NULL));
 
     /* enter scope */
-    vm_push_frame(th, class_iseq, VM_FRAME_MAGIC_CLASS,
+    cft = vm_push_frame(th, class_iseq, VM_FRAME_MAGIC_CLASS,
 		  klass, 0, VM_ENVVAL_BLOCK_PTR(GET_BLOCK_PTR()),
 		  class_iseq->iseq_encoded, GET_SP(),
 		  class_iseq->local_size, 0, class_iseq->stack_max);
+    cft->cklass = klass;
+
     RESTORE_REGS();
     NEXT_INSN();
 }
diff --git a/vm_core.h b/vm_core.h
index 8fd8ef4..32da076 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -529,6 +529,7 @@ typedef struct rb_control_frame_struct {
 #if VM_DEBUG_BP_CHECK
     VALUE *bp_check;		/* cfp[10] */
 #endif
+    VALUE cklass;
 } rb_control_frame_t;
 
 typedef struct rb_block_struct {
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index eb34119..b7e5794 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -287,6 +287,21 @@ vm_cref_push(rb_thread_t *th, VALUE klass, int noex, rb_block_t *blockptr)
     return cref;
 }
 
+static rb_control_frame_t *
+find_magic_class(rb_control_frame_t *frame)
+{
+    rb_thread_t *th = GET_THREAD();
+    rb_control_frame_t *cfp_limit;
+
+    cfp_limit = (rb_control_frame_t *)(th->stack + th->stack_size);
+    while (cfp_limit > frame) {
+        if (frame->flag == VM_FRAME_MAGIC_CLASS)
+            return frame;
+	frame = RUBY_VM_PREVIOUS_CONTROL_FRAME(frame);
+    }
+    return 0;
+}
+
 static inline VALUE
 vm_get_cbase(const rb_iseq_t *iseq, const VALUE *ep)
 {