diff --git a/ChangeLog b/ChangeLog
index 0f753b0828..f40f3eeefc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue May  3 04:27:53 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* thread.c (rb_thread_select): preserve errno if no error
+	  occurred.
+
 Tue May  3 03:57:04 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/intern.h (rb_w32_fdcopy): add prototype.  fixes
diff --git a/thread.c b/thread.c
index dd40be0ece..c272256d4b 100644
--- a/thread.c
+++ b/thread.c
@@ -2672,7 +2672,7 @@ rb_thread_select(int max, fd_set * read, fd_set * write, fd_set * except,
 	return 0;
     }
     else {
-	int lerrno;
+	int lerrno = errno;
 	int result;
 
 	BLOCKING_REGION({