diff --git a/beacon_chain/gossip_processing/block_processor.nim b/beacon_chain/gossip_processing/block_processor.nim
index 7c937dbafd..147cb4449c 100644
--- a/beacon_chain/gossip_processing/block_processor.nim
+++ b/beacon_chain/gossip_processing/block_processor.nim
@@ -13,6 +13,7 @@ import
   ../spec/[signatures, signatures_batch],
   ../sszdump
 
+from std/deques import Deque, addLast, contains, initDeque, items, len, shrink
 from ../consensus_object_pools/consensus_manager import
   ConsensusManager, checkNextProposer, optimisticExecutionPayloadHash,
   runProposalForkchoiceUpdated, shouldSyncOptimistically, updateHead,
@@ -47,6 +48,10 @@ const
     ## syncing the finalized part of the chain
   PAYLOAD_PRE_WALL_SLOTS = SLOTS_PER_EPOCH * 2
     ## Number of slots from wall time that we start processing every payload
+  MAX_DEDUP_QUEUE_LEN = 16
+    ## Number of blocks, with FIFO discipline, against which to check queued
+    ## blocks before being processed to avoid spamming ELs. This should stay
+    ## small enough that even O(n) algorithms are reasonable.
 
 type
   BlobSidecars* = seq[ref BlobSidecar]
@@ -103,6 +108,9 @@ type
       ## The slot at which we sent a payload to the execution client the last
       ## time
 
+    dupBlckBuf: Deque[(Eth2Digest, ValidatorSig)]
+      # Small buffer to allow for filtering of duplicate blocks in block queue
+
   NewPayloadStatus {.pure.} = enum
     valid
     notValid
@@ -140,7 +148,9 @@ proc new*(T: type BlockProcessor,
     validatorMonitor: validatorMonitor,
     blobQuarantine: blobQuarantine,
     getBeaconTime: getBeaconTime,
-    verifier: BatchVerifier(rng: rng, taskpool: taskpool)
+    verifier: BatchVerifier(rng: rng, taskpool: taskpool),
+    dupBlckBuf: initDeque[(Eth2Digest, ValidatorSig)](
+      initialSize = MAX_DEDUP_QUEUE_LEN)
   )
 
 # Sync callbacks
@@ -688,6 +698,19 @@ proc addBlock*(
   except AsyncQueueFullError:
     raiseAssert "unbounded queue"
 
+# Dedup
+# ------------------------------------------------------------------------------
+
+func checkDuplicateBlocks(self: ref BlockProcessor, entry: BlockEntry): bool =
+  let key = (entry.blck.root, entry.blck.signature)
+  if self.dupBlckBuf.contains key:
+    return true
+  doAssert self.dupBlckBuf.len <= MAX_DEDUP_QUEUE_LEN
+  if self.dupBlckBuf.len >= MAX_DEDUP_QUEUE_LEN:
+    self.dupBlckBuf.shrink(fromFirst = 1)
+  self.dupBlckBuf.addLast key
+  false
+
 # Event Loop
 # ------------------------------------------------------------------------------
 
@@ -704,6 +727,12 @@ proc processBlock(
     error "Processing block before genesis, clock turned back?"
     quit 1
 
+  if self.checkDuplicateBlocks(entry):
+    if entry.resfut != nil:
+      entry.resfut.complete(Result[void, VerifierError].err(
+        VerifierError.Duplicate))
+    return
+
   let res = withBlck(entry.blck):
     await self.storeBlock(
       entry.src, wallTime, blck, entry.blobs, entry.maybeFinalized,