diff --git a/ChangeLog b/ChangeLog
index fea153073e..79815d9076 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Tue Nov 27 09:29:11 2012  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread.c (thread_join): raises ThreadError if target therad
+	  is a main thread.
+	* test/ruby/test_thread.rb (test_thread_join_main_thread):
+	  test for the above.
+	* NEWS: news for the above.
+
 Tue Nov 27 09:24:47 2012  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* thread.c (thread_join): raises ThreadError if target thread
diff --git a/NEWS b/NEWS
index 7417fb0824..269fcbe2b6 100644
--- a/NEWS
+++ b/NEWS
@@ -160,7 +160,7 @@ with all sufficient information, see the ChangeLog file.
     * incompatible changes:
       * Thread#join no longer allows to be used from trap handler. Now it raises
         ThreadError.
-      * Thread#join raises ThreadError if target therad is a current thread.
+      * Thread#join raises ThreadError if target therad is a current or main thread. 
 
   * Time
     * change return value:
diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 95f2c89db4..fb2efec552 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -881,4 +881,12 @@ class TestThreadGroup < Test::Unit::TestCase
       Thread.current.join
     end
   end
+
+  def test_thread_join_main_thread
+    assert_raises(ThreadError) do
+      Thread.new(Thread.current) {|t|
+        t.join
+      }.join
+    end
+  end
 end
diff --git a/thread.c b/thread.c
index cdba4a2106..5214c68955 100644
--- a/thread.c
+++ b/thread.c
@@ -739,6 +739,9 @@ thread_join(rb_thread_t *target_th, double delay)
     if (th == target_th) {
 	rb_raise(rb_eThreadError, "Target thread must not be current thread");
     }
+    if (GET_VM()->main_thread == target_th) {
+	rb_raise(rb_eThreadError, "Target thread must not be main thread");
+    }
 
     arg.target = target_th;
     arg.waiting = th;