diff --git a/ergo-core/src/main/scala/org/ergoplatform/mining/AutolykosPowScheme.scala b/ergo-core/src/main/scala/org/ergoplatform/mining/AutolykosPowScheme.scala
index 5dd710da26..58a574c02f 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/mining/AutolykosPowScheme.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/mining/AutolykosPowScheme.scala
@@ -262,7 +262,7 @@ class AutolykosPowScheme(val k: Int, val n: Int) extends ScorexLogging {
     val (parentId, height) = AutolykosPowScheme.derivedHeaderFields(parentOpt)
 
     val h = HeaderWithoutPow(version, parentId, adProofsRoot, stateRoot, transactionsRoot, timestamp,
-      nBits, height, extensionHash, votes)
+      nBits, height, extensionHash, votes, Array.emptyByteArray)
     val msg = msgByHeader(h)
     val b = getB(nBits)
     val x = randomSecret()
diff --git a/ergo-core/src/main/scala/org/ergoplatform/mining/CandidateUtils.scala b/ergo-core/src/main/scala/org/ergoplatform/mining/CandidateUtils.scala
index 0ad1d87624..aee8cc3fc7 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/mining/CandidateUtils.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/mining/CandidateUtils.scala
@@ -29,7 +29,8 @@ object CandidateUtils {
       candidate.nBits,
       height,
       extensionRoot,
-      candidate.votes
+      candidate.votes,
+      Array.emptyByteArray
     )
   }
 }
diff --git a/ergo-core/src/main/scala/org/ergoplatform/mining/DefaultFakePowScheme.scala b/ergo-core/src/main/scala/org/ergoplatform/mining/DefaultFakePowScheme.scala
index 732bf25805..b6a3bdeff7 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/mining/DefaultFakePowScheme.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/mining/DefaultFakePowScheme.scala
@@ -33,7 +33,7 @@ class DefaultFakePowScheme(k: Int, n: Int) extends AutolykosPowScheme(k, n) {
     val d: BigInt = q / (height + 10)
     val s = AutolykosSolution(pk, w, n, d)
     Some(Header(version, parentId, adProofsRoot, stateRoot, transactionsRoot, timestamp,
-      nBits, height, extensionHash, s, votes))
+      nBits, height, extensionHash, s, votes, Array.emptyByteArray))
   }
 
   override def realDifficulty(header: Header): PrivateKey = header.requiredDifficulty
diff --git a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/Header.scala b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/Header.scala
index 092dcd219f..389d235066 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/Header.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/Header.scala
@@ -53,8 +53,9 @@ case class Header(override val version: Header.Version,
                   override val extensionRoot: Digest32,
                   powSolution: AutolykosSolution,
                   override val votes: Array[Byte], //3 bytes
+                  override val unparsedBytes: Array[Byte],
                   override val sizeOpt: Option[Int] = None) extends HeaderWithoutPow(version, parentId, ADProofsRoot, stateRoot, transactionsRoot, timestamp,
-  nBits, height, extensionRoot, votes) with PreHeader with BlockSection {
+  nBits, height, extensionRoot, votes, unparsedBytes) with PreHeader with BlockSection {
 
   override def serializedId: Array[Header.Version] = Algos.hash(bytes)
 
@@ -180,7 +181,8 @@ object Header extends ApiCodecs {
       "size" -> h.size.asJson,
       "extensionId" -> Algos.encode(h.extensionId).asJson,
       "transactionsId" -> Algos.encode(h.transactionsId).asJson,
-      "adProofsId" -> Algos.encode(h.ADProofsId).asJson
+      "adProofsId" -> Algos.encode(h.ADProofsId).asJson,
+      "unparsedBytes" -> Algos.encode(h.unparsedBytes).asJson
     ).asJson
   }
 
@@ -197,8 +199,10 @@ object Header extends ApiCodecs {
       version <- c.downField("version").as[Byte]
       votes <- c.downField("votes").as[String]
       solutions <- c.downField("powSolutions").as[AutolykosSolution]
+      unparsedBytes <- c.downField("unparsedBytes").as[Option[Array[Byte]]]
     } yield Header(version, parentId, adProofsRoot, stateRoot,
-      transactionsRoot, timestamp, nBits, height, extensionHash, solutions, Algos.decode(votes).get)
+      transactionsRoot, timestamp, nBits, height, extensionHash, solutions, Algos.decode(votes).get,
+      unparsedBytes.getOrElse(Array.emptyByteArray))
   }
 
 }
diff --git a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderSerializer.scala b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderSerializer.scala
index b6123e1141..bbe8829a05 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderSerializer.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderSerializer.scala
@@ -32,7 +32,8 @@ object HeaderSerializer extends ErgoSerializer[Header] {
     // For block version >= 2, this new byte encodes length of possible new fields.
     // Set to 0 for now, so no new fields.
     if (h.version > Header.InitialVersion) {
-      w.putUByte(0)
+      w.putUByte(h.unparsedBytes.length)
+      w.putBytes(h.unparsedBytes)
     }
   }
 
@@ -56,15 +57,19 @@ object HeaderSerializer extends ErgoSerializer[Header] {
 
     // For block version >= 2, a new byte encodes length of possible new fields.
     // If this byte > 0, we read new fields but do nothing, as semantics of the fields is not known.
-    if (version > Header.InitialVersion) {
+    val unparsedBytes = if (version > Header.InitialVersion) {
       val newFieldsSize = r.getUByte()
-      if (newFieldsSize > 0) {
+      if (newFieldsSize > 0) {  // todo: check protocol version?
         r.getBytes(newFieldsSize)
+      } else {
+        Array.emptyByteArray
       }
+    } else {
+      Array.emptyByteArray
     }
 
     HeaderWithoutPow(version, parentId, ADProofsRoot, stateRoot, transactionsRoot, timestamp,
-      nBits, height, extensionHash, votes)
+      nBits, height, extensionHash, votes, unparsedBytes)
   }
 
   override def parse(r: Reader): Header = {
diff --git a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderWithoutPow.scala b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderWithoutPow.scala
index ffe10380a2..067468f2c6 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderWithoutPow.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/HeaderWithoutPow.scala
@@ -17,19 +17,20 @@ class HeaderWithoutPow(val version: Header.Version, // 1 byte
                        val nBits: Long, //actually it is unsigned int
                        val height: Int,
                        val extensionRoot: Digest32,
-                       val votes: Array[Byte]) { //3 bytes
+                       val votes: Array[Byte], //3 bytes
+                       val unparsedBytes: Array[Byte]) {
   def toHeader(powSolution: AutolykosSolution, headerSize: Option[Int] = None): Header =
     Header(version, parentId, ADProofsRoot, stateRoot, transactionsRoot, timestamp,
-      nBits, height, extensionRoot, powSolution, votes, headerSize)
+      nBits, height, extensionRoot, powSolution, votes, unparsedBytes, headerSize)
 }
 
 object HeaderWithoutPow {
 
   def apply(version: Header.Version, parentId: ModifierId, ADProofsRoot: Digest32, stateRoot: ADDigest,
             transactionsRoot: Digest32, timestamp: Header.Timestamp, nBits: Long, height: Int,
-            extensionRoot: Digest32, votes: Array[Byte]): HeaderWithoutPow = {
+            extensionRoot: Digest32, votes: Array[Byte], unparsedBytes: Array[Byte]): HeaderWithoutPow = {
     new HeaderWithoutPow(version, parentId, ADProofsRoot, stateRoot, transactionsRoot, timestamp,
-      nBits, height, extensionRoot, votes)
+      nBits, height, extensionRoot, votes, unparsedBytes)
   }
 
 }
diff --git a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/PreGenesisHeader.scala b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/PreGenesisHeader.scala
index 7cebffbc5e..4924c63783 100644
--- a/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/PreGenesisHeader.scala
+++ b/ergo-core/src/main/scala/org/ergoplatform/modifiers/history/header/PreGenesisHeader.scala
@@ -18,6 +18,7 @@ object PreGenesisHeader extends Header(
   extensionRoot = null,
   powSolution = null,
   votes = null,
+  unparsedBytes = Array.emptyByteArray,
   sizeOpt = None) {
 
   override def serializedId: Array[Byte] = idToBytes(Header.GenesisParentId)
diff --git a/ergo-core/src/test/scala/org/ergoplatform/network/HeaderSerializationSpecification.scala b/ergo-core/src/test/scala/org/ergoplatform/network/HeaderSerializationSpecification.scala
index fb7821b255..f5445269a2 100644
--- a/ergo-core/src/test/scala/org/ergoplatform/network/HeaderSerializationSpecification.scala
+++ b/ergo-core/src/test/scala/org/ergoplatform/network/HeaderSerializationSpecification.scala
@@ -43,7 +43,7 @@ class HeaderSerializationSpecification extends ErgoCorePropertyTest {
     val votes = Array[Byte](4, 3, 0)
 
     val h = Header(version, parentId, adProofsRoot, stateRoot, transactionsRoot, timestamp, nBits,
-                    height, extensionRoot, powSolution, votes)
+                    height, extensionRoot, powSolution, votes, Array.emptyByteArray)
 
     h.id shouldBe "8cf6dca6b9505243e36192fa107735024c0000cf4594b1daa2dc4e13ee86f26f"
 
@@ -141,7 +141,7 @@ class HeaderSerializationSpecification extends ErgoCorePropertyTest {
     val votes = Array[Byte](0, 0, 0)
 
     val h = Header(version, parentId, adProofsRoot, stateRoot, transactionsRoot, timestamp, nBits,
-      height, extensionRoot, powSolution, votes)
+      height, extensionRoot, powSolution, votes, Array.emptyByteArray)
 
     h.id shouldBe "f46c89e44f13a92d8409341490f97f05c85785fa8d2d2164332cc066eda95c39"
 
diff --git a/ergo-core/src/test/scala/org/ergoplatform/utils/generators/ErgoCoreGenerators.scala b/ergo-core/src/test/scala/org/ergoplatform/utils/generators/ErgoCoreGenerators.scala
index 0cbb42425e..cadc6ae8b9 100644
--- a/ergo-core/src/test/scala/org/ergoplatform/utils/generators/ErgoCoreGenerators.scala
+++ b/ergo-core/src/test/scala/org/ergoplatform/utils/generators/ErgoCoreGenerators.scala
@@ -172,6 +172,7 @@ object ErgoCoreGenerators {
     extensionHash,
     powSolution,
     Array.fill(3)(0: Byte),
+    Array.emptyByteArray,
     None
   )
 
diff --git a/src/main/scala/org/ergoplatform/mining/CandidateGenerator.scala b/src/main/scala/org/ergoplatform/mining/CandidateGenerator.scala
index a42b50e6db..e7eb131d0d 100644
--- a/src/main/scala/org/ergoplatform/mining/CandidateGenerator.scala
+++ b/src/main/scala/org/ergoplatform/mining/CandidateGenerator.scala
@@ -903,7 +903,8 @@ object CandidateGenerator extends ScorexLogging {
       candidate.nBits,
       height,
       extensionRoot,
-      candidate.votes
+      candidate.votes,
+      Array.emptyByteArray
     )
   }