diff --git a/beacon_chain/gossip_processing/gossip_validation.nim b/beacon_chain/gossip_processing/gossip_validation.nim
index fab3bd0225..a56ecf54fb 100644
--- a/beacon_chain/gossip_processing/gossip_validation.nim
+++ b/beacon_chain/gossip_processing/gossip_validation.nim
@@ -293,9 +293,8 @@ template checkedReject(
     pool: ValidatorChangePool, error: ValidationError): untyped =
   pool.dag.checkedReject(error)
 
-func getMaxBlobsPerBlock(cfg: RuntimeConfig, wallTime: BeaconTime): uint64 =
-  if min(wallTime, wallTime - MAXIMUM_GOSSIP_CLOCK_DISPARITY).slotOrZero.epoch >=
-      cfg.ELECTRA_FORK_EPOCH:
+func getMaxBlobsPerBlock(cfg: RuntimeConfig, slot: Slot): uint64 =
+  if slot >= cfg.ELECTRA_FORK_EPOCH.start_slot:
     cfg.MAX_BLOBS_PER_BLOCK_ELECTRA
   else:
     MAX_BLOBS_PER_BLOCK
@@ -379,7 +378,7 @@ template validateBeaconBlockDeneb(
   # limitation defined in Consensus Layer -- i.e. validate that
   # len(body.signed_beacon_block.message.blob_kzg_commitments) <= MAX_BLOBS_PER_BLOCK
   if not (lenu64(signed_beacon_block.message.body.blob_kzg_commitments) <=
-      dag.cfg.getMaxBlobsPerBlock(wallTime)):
+      dag.cfg.getMaxBlobsPerBlock(signed_beacon_block.message.slot)):
     return dag.checkedReject("validateBeaconBlockDeneb: too many blob commitments")
 
 # https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.4/specs/deneb/p2p-interface.md#blob_sidecar_subnet_id
@@ -395,12 +394,13 @@ proc validateBlobSidecar*(
 
   # [REJECT] The sidecar's index is consistent with `MAX_BLOBS_PER_BLOCK`
   # -- i.e. `blob_sidecar.index < MAX_BLOBS_PER_BLOCK`
-  if not (blob_sidecar.index < dag.cfg.getMaxBlobsPerBlock(wallTime)):
+  if not (blob_sidecar.index < dag.cfg.getMaxBlobsPerBlock(block_header.slot)):
     return dag.checkedReject("BlobSidecar: index inconsistent")
 
   # [REJECT] The sidecar is for the correct subnet -- i.e.
   # `compute_subnet_for_blob_sidecar(blob_sidecar.index) == subnet_id`.
-  if not (compute_subnet_for_blob_sidecar(blob_sidecar.index) == subnet_id):
+  if not (dag.cfg.compute_subnet_for_blob_sidecar(
+      block_header.slot, blob_sidecar.index) == subnet_id):
     return dag.checkedReject("BlobSidecar: subnet incorrect")
 
   # [IGNORE] The sidecar is not from a future slot (with a
diff --git a/beacon_chain/spec/network.nim b/beacon_chain/spec/network.nim
index 56deffe557..62bc1b9e36 100644
--- a/beacon_chain/spec/network.nim
+++ b/beacon_chain/spec/network.nim
@@ -110,9 +110,16 @@ func getBlobSidecarTopic*(forkDigest: ForkDigest,
                           subnet_id: BlobId): string =
   eth2Prefix(forkDigest) & "blob_sidecar_" & $subnet_id & "/ssz_snappy"
 
-# https://github.com/ethereum/consensus-specs/blob/v1.4.0/specs/deneb/validator.md#sidecar
-func compute_subnet_for_blob_sidecar*(blob_index: BlobIndex): BlobId =
-  BlobId(blob_index mod MAX_BLOBS_PER_BLOCK_ELECTRA)
+# https://github.com/ethereum/consensus-specs/blob/v1.5.0-beta.2/specs/deneb/validator.md#sidecar
+# https://github.com/ethereum/consensus-specs/blob/v1.5.0-beta.2/specs/electra/validator.md#sidecar
+func compute_subnet_for_blob_sidecar*(
+    cfg: RuntimeConfig, slot: Slot, blob_index: BlobIndex): BlobId =
+  let subnetCount =
+    if slot >= cfg.ELECTRA_FORK_EPOCH.start_slot:
+      cfg.BLOB_SIDECAR_SUBNET_COUNT_ELECTRA
+    else:
+      BLOB_SIDECAR_SUBNET_COUNT
+  BlobId(blob_index mod subnetCount)
 
 # https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.10/specs/fulu/p2p-interface.md#compute_subnet_for_data_column_sidecar
 func compute_subnet_for_data_column_sidecar*(column_index: ColumnIndex): uint64 =
diff --git a/beacon_chain/validators/message_router.nim b/beacon_chain/validators/message_router.nim
index 0965453b9f..31c9fca380 100644
--- a/beacon_chain/validators/message_router.nim
+++ b/beacon_chain/validators/message_router.nim
@@ -1,5 +1,5 @@
 # beacon_chain
-# Copyright (c) 2018-2024 Status Research & Development GmbH
+# Copyright (c) 2018-2025 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).
@@ -157,7 +157,9 @@ proc routeSignedBeaconBlock*(
     let blobs = blobsOpt.get()
     var workers = newSeq[Future[SendResult]](blobs.len)
     for i in 0..<blobs.lenu64:
-      let subnet_id = compute_subnet_for_blob_sidecar(i)
+      let subnet_id = router[].processor[]
+        .dag.cfg.compute_subnet_for_blob_sidecar(
+          blobs[i].signed_block_header.message.slot, i)
       workers[i] = router[].network.broadcastBlobSidecar(subnet_id, blobs[i])
     let allres = await allFinished(workers)
     for i in 0..<allres.len: