diff --git a/ChangeLog b/ChangeLog
index c1a9c73d5d..fc412346b1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jul 14 09:26:14 2009  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
+
+	* ext/tk/lib/multi-tk.rb: Long-term-callback support isn't stable yet.
+	  So, disable the feature and waiting for improvement in the future.
+
 Mon Jul 13 08:01:00 2009  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/extconf.rb: New strategy for searching Tcl/Tk libraries.
diff --git a/ext/tk/lib/multi-tk.rb b/ext/tk/lib/multi-tk.rb
index c10c349d05..c491d0c7ba 100644
--- a/ext/tk/lib/multi-tk.rb
+++ b/ext/tk/lib/multi-tk.rb
@@ -2182,7 +2182,8 @@ class MultiTkIp
   end
   private :eval_proc_core
 
-if WITH_RUBY_VM  ### Ruby 1.9
+if false && WITH_RUBY_VM  ### Ruby 1.9
+  # Not stable, so disable this feature
   def eval_callback(*args)
     if block_given?
       cmd = Proc.new
diff --git a/ext/tk/sample/safe-tk.rb b/ext/tk/sample/safe-tk.rb
index 148548efb2..2aeae235df 100644
--- a/ext/tk/sample/safe-tk.rb
+++ b/ext/tk/sample/safe-tk.rb
@@ -81,7 +81,7 @@ p ip.eval_proc(proc{
                               :command=>proc{
                                 MultiTkIp._proc_on_current_safelevel(y).call(l)
                               }).pack(:fill=>:x, :padx=>5)
-if Object.const_defined?(:RubyVM) && ::RubyVM.class == Class
+if false && Object.const_defined?(:RubyVM) && ::RubyVM.class == Class
                  TkButton.new(:text=>':command=>proc{Thread.new(l, &y).value}',
                               :command=>proc{
                                 Thread.new(l, &y).value