diff --git a/ChangeLog b/ChangeLog
index 6a3001fae5..975b00972c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Fri Dec 21 20:38:28 2012  Koichi Sasada  <ko1@atdot.net>
+
+	* iseq.c (Init_ISeq): remove definition of the following methods:
+	  ISeq#line_trace_all and ISeq#line_trace_specify because they are
+	  half baked.
+	  C APIs are remained as experimental. These functions will be
+	  renamed, removed their parameters may be changed.
+	  You can use these methods by C exts. Please give us your comments.
+
 Fri Dec 21 20:21:04 2012  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_trace.c (tracepoint_new): add code to support specified thread.
diff --git a/iseq.c b/iseq.c
index 9fb82d49c6..2394691731 100644
--- a/iseq.c
+++ b/iseq.c
@@ -2076,9 +2076,15 @@ Init_ISeq(void)
     rb_define_method(rb_cISeq, "base_label", iseq_base_label, 0);
     rb_define_method(rb_cISeq, "first_lineno", iseq_first_lineno, 0);
 
-    /* experimental */
+#if 0
+    /* Now, it is experimental. No discussions, no tests. */
+    /* They can be used from C level. Please give us feedback. */
     rb_define_method(rb_cISeq, "line_trace_all", rb_iseq_line_trace_all, 0);
     rb_define_method(rb_cISeq, "line_trace_specify", rb_iseq_line_trace_specify, 2);
+#else
+    (void)rb_iseq_line_trace_all;
+    (void)rb_iseq_line_trace_specify;
+#endif
 
 #if 0 /* TBD */
     rb_define_private_method(rb_cISeq, "marshal_dump", iseq_marshal_dump, 0);