diff --git a/ChangeLog b/ChangeLog
index 724fdc626e..63773b9857 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Dec 17 19:39:44 2008  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/socket.c (unix_recv_io): relax msg_controllen error
+	  check.
+
 Wed Dec 17 19:37:30 2008  Tanaka Akira  <akr@fsij.org>
 
 	* ext/pty/extconf.rb: check util.h for OpenBSD.
diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index 2f7a07f864..a8b53bd534 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -2118,9 +2118,14 @@ unix_recv_io(int argc, VALUE *argv, VALUE sock)
 	rb_sys_fail("recvmsg(2)");
 
 #if FD_PASSING_BY_MSG_CONTROL
-    if (arg.msg.msg_controllen != CMSG_SPACE(sizeof(int))) {
+    if (arg.msg.msg_controllen < CMSG_LEN(sizeof(int))) {
 	rb_raise(rb_eSocket,
-		 "file descriptor was not passed (msg_controllen=%d, %d expected)",
+		 "file descriptor was not passed (msg_controllen=%d smaller than CMSG_LEN(sizeof(int))=%d)",
+		 (int)arg.msg.msg_controllen, (int)CMSG_LEN(sizeof(int)));
+    }
+    if (CMSG_SPACE(sizeof(int)) < arg.msg.msg_controllen) {
+	rb_raise(rb_eSocket,
+		 "file descriptor was not passed (msg_controllen=%d bigger than CMSG_SPACE(sizeof(int))=%d)",
 		 (int)arg.msg.msg_controllen, (int)CMSG_SPACE(sizeof(int)));
     }
     if (cmsg.hdr.cmsg_len != CMSG_LEN(sizeof(int))) {