diff --git a/beacon_chain/eth1/eth1_monitor.nim b/beacon_chain/eth1/eth1_monitor.nim
index 249e2da2d..b4aae8fe3 100644
--- a/beacon_chain/eth1/eth1_monitor.nim
+++ b/beacon_chain/eth1/eth1_monitor.nim
@@ -412,8 +412,8 @@ proc getBlockByNumber*(p: Web3DataProviderRef,
   p.web3.provider.eth_getBlockByNumber(hexNumber, false)
 
 proc getPayload*(p: Web3DataProviderRef,
-                 payloadId: Quantity): Future[engine_api.ExecutionPayloadV1] =
-  p.web3.provider.engine_getPayloadV1(payloadId)
+                 payloadId: merge.PayloadID): Future[engine_api.ExecutionPayloadV1] =
+  p.web3.provider.engine_getPayloadV1(FixedBytes[8] payloadId)
 
 proc executePayload*(p: Web3DataProviderRef,
                      payload: engine_api.ExecutionPayloadV1): Future[ExecutePayloadResponse] =
diff --git a/beacon_chain/spec/datatypes/merge.nim b/beacon_chain/spec/datatypes/merge.nim
index 4f5d13f09..d1723bfa6 100644
--- a/beacon_chain/spec/datatypes/merge.nim
+++ b/beacon_chain/spec/datatypes/merge.nim
@@ -40,6 +40,8 @@ type
   BloomLogs* = object
     data*: array[BYTES_PER_LOGS_BLOOM, byte]
 
+  PayloadID* = array[8, byte]
+
   # https://github.com/ethereum/consensus-specs/blob/v1.1.3/specs/merge/beacon-chain.md#executionpayload
   ExecutionPayload* = object
     parent_hash*: Eth2Digest
diff --git a/tests/test_merge_vectors.nim b/tests/test_merge_vectors.nim
index d05d320b2..7eedb46d8 100644
--- a/tests/test_merge_vectors.nim
+++ b/tests/test_merge_vectors.nim
@@ -12,7 +12,7 @@ import
 
 suite "Merge test vectors":
   let web3Provider = (waitFor Web3DataProvider.new(
-    default(Eth1Address), "ws://127.0.0.1:8546")).get
+    default(Eth1Address), "ws://127.0.0.1:8551")).get
 
   test "getPayload, executePayload, and forkchoiceUpdated":
     const feeRecipient =
@@ -26,7 +26,7 @@ suite "Merge test vectors":
         default(Eth2Digest).data,  # Random
         feeRecipient)
       payload =         waitFor web3Provider.getPayload(
-        Quantity(payloadId.payloadId.get))
+        array[8, byte] (payloadId.payloadId.get))
       payloadStatus =   waitFor web3Provider.executePayload(payload)
       fcupdatedStatus = waitFor web3Provider.forkchoiceUpdated(
         payload.blockHash.asEth2Digest,
@@ -36,7 +36,7 @@ suite "Merge test vectors":
         feeRecipient)
 
       payload2 =         waitFor web3Provider.getPayload(
-        Quantity(fcupdatedStatus.payloadId.get))
+        array[8, byte] (fcupdatedStatus.payloadId.get))
       payloadStatus2 =   waitFor web3Provider.executePayload(payload2)
       fcupdatedStatus2 = waitFor web3Provider.forkchoiceUpdated(
         payload2.blockHash.asEth2Digest,
diff --git a/vendor/nim-web3 b/vendor/nim-web3
index 183cc8f40..41fc21595 160000
--- a/vendor/nim-web3
+++ b/vendor/nim-web3
@@ -1 +1 @@
-Subproject commit 183cc8f407082a44fec18492a8c18a8261cdd27f
+Subproject commit 41fc21595c1882ee4aaa92217f9d8d950864f9f2