diff --git a/ChangeLog b/ChangeLog
index a3c8cbd47c..273a8cb19f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Wed Nov 18 06:59:52 2015  Eric Wong  <e@80x24.org>
+
+	* ext/socket/ancdata.c (bsock_recvmsg_internal): grow buffer
+	  on unspecified maxdatlen
+	  [ruby-core:71517] [Bug #11701]
+	* ext/socket/lib/socket.rb (Socket#recvmsg): nil default for dlen
+	  (Socket#recvmsg_nonblock): ditto
+	* test/socket/test_socket.rb (test_recvmsg_udp_no_arg): new test
+
 Tue Nov 17 19:50:06 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* win32/win32.c (fstat): declare for mingw.
diff --git a/ext/socket/ancdata.c b/ext/socket/ancdata.c
index 168f70c311..8fcd53c9fb 100644
--- a/ext/socket/ancdata.c
+++ b/ext/socket/ancdata.c
@@ -1465,7 +1465,7 @@ bsock_recvmsg_internal(VALUE sock,
     int gc_done = 0;
 #endif
 
-    maxdatlen = NUM2SIZET(vmaxdatlen);
+    maxdatlen = NIL_P(vmaxdatlen) ? 4061 : NUM2SIZET(vmaxdatlen);
 #if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)
     maxctllen = NIL_P(vmaxctllen) ? 4096 : NUM2SIZET(vmaxctllen);
 #else
diff --git a/ext/socket/lib/socket.rb b/ext/socket/lib/socket.rb
index 58e7dfd92a..0240c2094e 100644
--- a/ext/socket/lib/socket.rb
+++ b/ext/socket/lib/socket.rb
@@ -425,7 +425,7 @@ class BasicSocket < IO
   #       return ancdata.unix_rights[0]
   #     end
   #   }
-  def recvmsg(dlen = 4096, flags = 0, clen = nil, scm_rights: false)
+  def recvmsg(dlen = nil, flags = 0, clen = nil, scm_rights: false)
     __recvmsg(dlen, flags, clen, scm_rights)
   end
 
@@ -441,7 +441,7 @@ class BasicSocket < IO
   # By specifying `exception: false`, the _opts_ hash allows you to indicate
   # that recvmsg_nonblock should not raise an IO::WaitWritable exception, but
   # return the symbol :wait_writable instead.
-  def recvmsg_nonblock(dlen = 4096, flags = 0, clen = nil,
+  def recvmsg_nonblock(dlen = nil, flags = 0, clen = nil,
                        scm_rights: false, exception: true)
     __recvmsg_nonblock(dlen, flags, clen, scm_rights, exception)
   end
diff --git a/test/socket/test_socket.rb b/test/socket/test_socket.rb
index 26684622e2..bfa4a143bf 100644
--- a/test/socket/test_socket.rb
+++ b/test/socket/test_socket.rb
@@ -653,4 +653,20 @@ class TestSocket < Test::Unit::TestCase
     end
   end
 
+  def test_recvmsg_udp_no_arg
+    n = 4097
+    s1 = Addrinfo.udp("127.0.0.1", 0).bind
+    s2 = s1.connect_address.connect
+    s2.send("a" * n, 0)
+    ret = s1.recvmsg
+    assert_equal n, ret[0].bytesize, '[ruby-core:71517] [Bug #11701]'
+
+    s2.send("a" * n, 0)
+    IO.select([s1])
+    ret = s1.recvmsg_nonblock
+    assert_equal n, ret[0].bytesize, 'non-blocking should also grow'
+  ensure
+    s1.close
+    s2.close
+  end
 end if defined?(Socket)