diff --git a/fluffy/network/history/content/content_values.nim b/fluffy/network/history/content/content_values.nim
index 311ad8e076..a2f93d294c 100644
--- a/fluffy/network/history/content/content_values.nim
+++ b/fluffy/network/history/content/content_values.nim
@@ -26,25 +26,15 @@ const
   MAX_WITHDRAWALS_COUNT = MAX_WITHDRAWALS_PER_PAYLOAD
 
   MAX_EPHEMERAL_HEADER_PAYLOAD = 256
+  MAX_HEADER_PROOF_LENGTH* = 1024
 
 type
   ## BlockHeader types
   HistoricalHashesAccumulatorProof* = array[15, Digest]
 
-  BlockHeaderProofType* = enum
-    none = 0x00 # An SSZ Union None
-    historicalHashesAccumulatorProof = 0x01
-
-  BlockHeaderProof* = object
-    case proofType*: BlockHeaderProofType
-    of none:
-      discard
-    of historicalHashesAccumulatorProof:
-      historicalHashesAccumulatorProof*: HistoricalHashesAccumulatorProof
-
   BlockHeaderWithProof* = object
     header*: ByteList[MAX_HEADER_LENGTH] # RLP data
-    proof*: BlockHeaderProof
+    proof*: ByteList[MAX_HEADER_PROOF_LENGTH]
 
   ## Ephemeral BlockHeader list
   EphemeralBlockHeaderList* =
@@ -73,11 +63,3 @@ type
   ## Receipts types
   ReceiptByteList* = ByteList[MAX_RECEIPT_LENGTH] # RLP data
   PortalReceipts* = List[ReceiptByteList, MAX_TRANSACTION_COUNT]
-
-func init*(T: type BlockHeaderProof, proof: HistoricalHashesAccumulatorProof): T =
-  BlockHeaderProof(
-    proofType: historicalHashesAccumulatorProof, historicalHashesAccumulatorProof: proof
-  )
-
-func init*(T: type BlockHeaderProof): T =
-  BlockHeaderProof(proofType: none)
diff --git a/fluffy/network/history/history_validation.nim b/fluffy/network/history/history_validation.nim
index aa7d76b36a..85cd6806c5 100644
--- a/fluffy/network/history/history_validation.nim
+++ b/fluffy/network/history/history_validation.nim
@@ -50,20 +50,23 @@ func validateHeaderBytes*(
   ok(header)
 
 func verifyBlockHeaderProof*(
-    a: FinishedHistoricalHashesAccumulator, header: Header, proof: BlockHeaderProof
+    a: FinishedHistoricalHashesAccumulator,
+    header: Header,
+    proof: ByteList[MAX_HEADER_PROOF_LENGTH],
 ): Result[void, string] =
-  case proof.proofType
-  of BlockHeaderProofType.historicalHashesAccumulatorProof:
-    a.verifyAccumulatorProof(header, proof.historicalHashesAccumulatorProof)
-  of BlockHeaderProofType.none:
-    if header.isPreMerge():
-      err("Pre merge header requires HistoricalHashesAccumulatorProof")
-    else:
-      # TODO:
-      # Add verification post merge based on historical_roots & historical_summaries
-      # Lets for now no longer accept other headers without a proof and the most
-      # recent ones are now a different type.
-      err("Post merge header proofs not yet activated")
+  let timestamp = Moment.init(header.timestamp.int64, Second)
+
+  if isShanghai(chainConfig, timestamp):
+    # TODO: Add verification post merge based on historical_summaries
+    err("Shanghai block verification not implemented")
+  elif isPoSBlock(chainConfig, header.number):
+    # TODO: Add verification post merge based on historical_roots
+    err("PoS block verification not implemented")
+  else:
+    let accumulatorProof = decodeSsz(proof.asSeq(), HistoricalHashesAccumulatorProof).valueOr:
+      return err("Failed decoding accumulator proof: " & error)
+
+    a.verifyAccumulatorProof(header, accumulatorProof)
 
 func validateCanonicalHeaderBytes*(
     bytes: openArray[byte], id: uint64 | Hash32, a: FinishedHistoricalHashesAccumulator
diff --git a/fluffy/network/history/validation/historical_hashes_accumulator.nim b/fluffy/network/history/validation/historical_hashes_accumulator.nim
index a6979aeced..0b9c07086a 100644
--- a/fluffy/network/history/validation/historical_hashes_accumulator.nim
+++ b/fluffy/network/history/validation/historical_hashes_accumulator.nim
@@ -1,5 +1,5 @@
 # Nimbus
-# Copyright (c) 2022-2024 Status Research & Development GmbH
+# Copyright (c) 2022-2025 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -198,7 +198,7 @@ func buildHeaderWithProof*(
 
   ok(
     BlockHeaderWithProof(
-      header: ByteList[2048].init(rlp.encode(header)),
-      proof: BlockHeaderProof.init(proof),
+      header: ByteList[MAX_HEADER_LENGTH].init(rlp.encode(header)),
+      proof: ByteList[MAX_HEADER_PROOF_LENGTH].init(SSZ.encode(proof)),
     )
   )
diff --git a/fluffy/tests/rpc_tests/test_portal_rpc_client.nim b/fluffy/tests/rpc_tests/test_portal_rpc_client.nim
index bb8b9a6b96..466d16f09c 100644
--- a/fluffy/tests/rpc_tests/test_portal_rpc_client.nim
+++ b/fluffy/tests/rpc_tests/test_portal_rpc_client.nim
@@ -1,5 +1,5 @@
 # Nimbus - Portal Network
-# Copyright (c) 2021-2024 Status Research & Development GmbH
+# Copyright (c) 2021-2025 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -63,7 +63,8 @@ proc store*(hn: HistoryNode, blockHash: Hash32, blockHeader: Header) =
   let
     headerRlp = rlp.encode(blockHeader)
     blockHeaderWithProof = BlockHeaderWithProof(
-      header: ByteList[2048].init(headerRlp), proof: BlockHeaderProof.init()
+      header: ByteList[MAX_HEADER_LENGTH].init(headerRlp),
+      proof: ByteList[MAX_HEADER_PROOF_LENGTH].init(@[]),
     )
     contentKeyBytes = blockHeaderContentKey(blockHash).encode()
     contentId = history_content.toContentId(contentKeyBytes)
diff --git a/fluffy/tests/state_network_tests/state_test_helpers.nim b/fluffy/tests/state_network_tests/state_test_helpers.nim
index 01d76faef9..9fd3e3f2f4 100644
--- a/fluffy/tests/state_network_tests/state_test_helpers.nim
+++ b/fluffy/tests/state_network_tests/state_test_helpers.nim
@@ -1,5 +1,5 @@
 # Fluffy
-# Copyright (c) 2021-2024 Status Research & Development GmbH
+# Copyright (c) 2021-2025 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
@@ -154,7 +154,8 @@ proc mockStateRootLookup*(
     blockHeader = Header(stateRoot: stateRoot)
     headerRlp = rlp.encode(blockHeader)
     blockHeaderWithProof = BlockHeaderWithProof(
-      header: ByteList[2048].init(headerRlp), proof: BlockHeaderProof.init()
+      header: ByteList[MAX_HEADER_LENGTH].init(headerRlp),
+      proof: ByteList[MAX_HEADER_PROOF_LENGTH].init(@[]),
     )
     contentKeyBytes = blockHeaderContentKey(blockNumOrHash).encode()
     contentId = history_content.toContentId(contentKeyBytes)