diff --git a/ChangeLog b/ChangeLog
index 838faa99ff..e54eb911fb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Nov 19 02:52:30 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/ancdata.c (bsock_recvmsg_internal): stretch the buffer size
+	  only when vmaxdatlen is nil.
+
 Thu Nov 19 02:20:11 2015  Tanaka Akira  <akr@fsij.org>
 
 	* test/socket/test_socket.rb (test_udp_recvmsg_truncation): rflags is
diff --git a/ext/socket/ancdata.c b/ext/socket/ancdata.c
index 1a6b50958c..93615f2766 100644
--- a/ext/socket/ancdata.c
+++ b/ext/socket/ancdata.c
@@ -1571,7 +1571,7 @@ bsock_recvmsg_internal(VALUE sock,
 	    goto retry;
         }
 #else
-	if (grow_buffer && errno == EMSGSIZE)
+	if (NIL_P(vmaxdatlen) && grow_buffer && errno == EMSGSIZE)
 	    ss = (ssize_t)iov.iov_len;
 	else
 #endif