diff --git a/ChangeLog b/ChangeLog
index cdacfb7ea2..cedb50a235 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Mon Aug 13 05:03:53 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* thread.c (rb_thread_raise): check if target thread is
+	  thrown by another thread or not.  [ruby-dev:31371]
+
+	* bootstraptest/test_thread.rb: add a test for above.
+
 Mon Aug 13 04:35:30 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* compile.c (iseq_peephole_optimize): fix peephole optimization
@@ -5,7 +12,6 @@ Mon Aug 13 04:35:30 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* bootstraptest/test_syntax.rb: add a test for above.
 
-
 Mon Aug 13 04:02:29 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_dump.c (debug_print_pre): fix to show control frame count.
diff --git a/bootstraptest/test_thread.rb b/bootstraptest/test_thread.rb
index 64d685fa19..40ccbad497 100644
--- a/bootstraptest/test_thread.rb
+++ b/bootstraptest/test_thread.rb
@@ -169,3 +169,17 @@ assert_equal %q{11}, %q{
     Thread.current[:a]
   }.value + Thread.current[:a]
 }
+assert_equal %q{1000}, %q{
+begin
+  1000.times do |i|
+    begin
+      Thread.start(Thread.current) {|u| u.raise }
+      raise
+    rescue
+    ensure
+    end
+  end
+rescue
+  1000
+end
+}, '[ruby-dev:31371]'
diff --git a/thread.c b/thread.c
index 7ff9439cf4..bae2fd7555 100644
--- a/thread.c
+++ b/thread.c
@@ -758,12 +758,17 @@ rb_thread_raise(int argc, VALUE *argv, rb_thread_t *th)
 {
     VALUE exc;
 
+  again:
     if (rb_thread_dead(th)) {
 	return Qnil;
     }
 
+    if (th->thrown_errinfo != 0 || th->raised_flag) {
+	rb_thread_schedule();
+	goto again;
+    }
+
     exc = rb_make_exception(argc, argv);
-    /* TODO: need synchronization if run threads in parallel */
     th->thrown_errinfo = exc;
     rb_thread_ready(th);
     return Qnil;