diff --git a/ChangeLog b/ChangeLog
index ca43192020..920e36c0b8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Thu Oct 15 09:25:07 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+ * ext/socket/init.c (rsock_init_sock): mswin doesn't have S_IFSOCK
+   flag in st_mode of struct stat. so, use rb_w32_issocket() function
+   instead of S_ISSOCK macro.
+
+Thu Oct 15 00:26:07 2009  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/init.c (rsock_init_sock): validate file descriptor.
+
 Tue Oct 13 18:54:25 2009  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/variable.rb: bug fix. additional trace definition changes the
diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index 73a02d15f3..a7c5948b69 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -52,6 +52,9 @@
 #ifdef HAVE_SYS_UN_H
 #include <sys/un.h>
 #endif
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
 
 #if defined(HAVE_FCNTL)
 #ifdef HAVE_SYS_SELECT_H
@@ -237,6 +240,17 @@ static VALUE
 init_sock(VALUE sock, int fd)
 {
     rb_io_t *fp;
+    struct stat sbuf;
+    
+#ifndef _WIN32
+    if (fstat(fd, &sbuf) < 0)
+	rb_sys_fail(0);
+    if (!S_ISSOCK(sbuf.st_mode))
+	rb_raise(rb_eArgError, "not a socket file descriptor");
+#else
+    if (!rb_w32_is_socket(fd))
+	rb_raise(rb_eArgError, "not a socket file descriptor");
+#endif
 
     MakeOpenFile(sock, fp);
     fp->fd = fd;
diff --git a/version.h b/version.h
index 8178e55943..6a54938076 100644
--- a/version.h
+++ b/version.h
@@ -1,5 +1,5 @@
 #define RUBY_VERSION "1.9.1"
-#define RUBY_PATCHLEVEL 391
+#define RUBY_PATCHLEVEL 392
 #define RUBY_VERSION_MAJOR 1
 #define RUBY_VERSION_MINOR 9
 #define RUBY_VERSION_TEENY 1