diff --git a/ChangeLog b/ChangeLog
index 0fca5a1013..2ab4c9086a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Apr  1 04:50:44 2016  Eric Wong  <e@80x24.org>
+
+	* ext/openssl/ossl_ssl.c (ossl_sslctx_s_alloc):
+	  enable SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER by default
+	  [Bug #12126]
+
 Fri Apr  1 01:13:55 2016  Benoit Daloze  <eregontp@gmail.com>
 
 	* thread.c (update_coverage): Do not track coverage in loaded files
diff --git a/ext/openssl/ossl_ssl.c b/ext/openssl/ossl_ssl.c
index 0e01d7c0b1..5fcd2145c3 100644
--- a/ext/openssl/ossl_ssl.c
+++ b/ext/openssl/ossl_ssl.c
@@ -145,7 +145,8 @@ static VALUE
 ossl_sslctx_s_alloc(VALUE klass)
 {
     SSL_CTX *ctx;
-    long mode = SSL_MODE_ENABLE_PARTIAL_WRITE;
+    long mode = SSL_MODE_ENABLE_PARTIAL_WRITE |
+	SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER;
     VALUE obj;
 
 #ifdef SSL_MODE_RELEASE_BUFFERS
diff --git a/test/openssl/test_pair.rb b/test/openssl/test_pair.rb
index 06ed3836ca..06c34442b7 100644
--- a/test/openssl/test_pair.rb
+++ b/test/openssl/test_pair.rb
@@ -280,6 +280,35 @@ module OpenSSL::TestPairM
     }
   end
 
+  def test_write_nonblock_retry
+    ssl_pair {|s1, s2|
+      # fill up a socket so we hit EAGAIN
+      written = String.new
+      n = 0
+      buf = 'a' * 11
+      case ret = s1.write_nonblock(buf, exception: false)
+      when :wait_readable then break
+      when :wait_writable then break
+      when Integer
+        written << buf
+        n += ret
+        exp = buf.bytesize
+        if ret != exp
+          buf = buf.byteslice(ret, exp - ret)
+        end
+      end while true
+      assert_kind_of Symbol, ret
+
+      # make more space for subsequent write:
+      readed = s2.read(n)
+      assert_equal written, readed
+
+      # this fails if SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER is missing:
+      buf2 = Marshal.load(Marshal.dump(buf))
+      assert_kind_of Integer, s1.write_nonblock(buf2, exception: false)
+    }
+  end
+
   def tcp_pair
     host = "127.0.0.1"
     serv = TCPServer.new(host, 0)