diff --git a/src/cryptonote_core/tx_extra.h b/src/cryptonote_core/tx_extra.h
index 8cff085dc..254a6a2ff 100644
--- a/src/cryptonote_core/tx_extra.h
+++ b/src/cryptonote_core/tx_extra.h
@@ -11,6 +11,7 @@
 #define TX_EXTRA_TAG_PADDING                0x00
 #define TX_EXTRA_TAG_PUBKEY                 0x01
 #define TX_EXTRA_NONCE                      0x02
+#define TX_EXTRA_MERGE_MINING_TAG           0x03
 
 #define TX_EXTRA_NONCE_PAYMENT_ID           0x00
 
@@ -82,13 +83,63 @@ namespace cryptonote
     END_SERIALIZE()
   };
 
+  struct tx_extra_merge_mining_tag
+  {
+    struct serialize_helper
+    {
+      tx_extra_merge_mining_tag& mm_tag;
+
+      serialize_helper(tx_extra_merge_mining_tag& mm_tag_) : mm_tag(mm_tag_)
+      {
+      }
+
+      BEGIN_SERIALIZE()
+        VARINT_FIELD_N("depth", mm_tag.depth)
+        FIELD_N("merkle_root", mm_tag.merkle_root)
+      END_SERIALIZE()
+    };
+
+    size_t depth;
+    crypto::hash merkle_root;
+
+    // load
+    template <template <bool> class Archive>
+    bool do_serialize(Archive<false>& ar)
+    {
+      std::string field;
+      if(!::do_serialize(ar, field))
+        return false;
+
+      std::istringstream iss(field);
+      binary_archive<false> iar(iss);
+      serialize_helper helper(*this);
+      return ::serialization::serialize(iar, helper);
+    }
+
+    // store
+    template <template <bool> class Archive>
+    bool do_serialize(Archive<true>& ar)
+    {
+      std::ostringstream oss;
+      binary_archive<true> oar(oss);
+      serialize_helper helper(*this);
+      if(!::do_serialize(oar, helper))
+        return false;
+
+      std::string field = oss.str();
+      return ::serialization::serialize(ar, field);
+    }
+  };
+
   // tx_extra_field format, except tx_extra_padding and tx_extra_pub_key:
   //   varint tag;
   //   varint size;
   //   varint data[];
-  typedef boost::variant<tx_extra_padding, tx_extra_pub_key, tx_extra_nonce> tx_extra_field;
+  //typedef boost::variant<tx_extra_padding, tx_extra_pub_key, tx_extra_nonce> tx_extra_field;
+  typedef boost::variant<tx_extra_padding, tx_extra_pub_key, tx_extra_nonce, tx_extra_merge_mining_tag> tx_extra_field;
 }
 
 VARIANT_TAG(binary_archive, cryptonote::tx_extra_padding, TX_EXTRA_TAG_PADDING);
 VARIANT_TAG(binary_archive, cryptonote::tx_extra_pub_key, TX_EXTRA_TAG_PUBKEY);
 VARIANT_TAG(binary_archive, cryptonote::tx_extra_nonce, TX_EXTRA_NONCE);
+VARIANT_TAG(binary_archive, cryptonote::tx_extra_merge_mining_tag, TX_EXTRA_MERGE_MINING_TAG);