diff --git a/packages/api/src/builder/routes.ts b/packages/api/src/builder/routes.ts
index a203a93b8af..a044c1418f1 100644
--- a/packages/api/src/builder/routes.ts
+++ b/packages/api/src/builder/routes.ts
@@ -71,7 +71,7 @@ export type Endpoints = {
 
   submitBlindedBlock: Endpoint<
     "POST",
-    {signedBlindedBlock: SignedBlindedBeaconBlock},
+    {signedBlindedBlock: SignedBlindedBeaconBlock; sszBytes?: Uint8Array | null},
     {body: unknown; headers: {[MetaHeader.Version]: string}},
     ExecutionPayload | ExecutionPayloadAndBlobsBundle,
     VersionMeta
@@ -138,10 +138,10 @@ export function getDefinitions(config: ChainForkConfig): RouteDefinitions<Endpoi
             signedBlindedBlock: getExecutionForkTypes(fork).SignedBlindedBeaconBlock.fromJson(body),
           };
         },
-        writeReqSsz: ({signedBlindedBlock}) => {
+        writeReqSsz: ({signedBlindedBlock, sszBytes}) => {
           const fork = config.getForkName(signedBlindedBlock.message.slot);
           return {
-            body: getExecutionForkTypes(fork).SignedBlindedBeaconBlock.serialize(signedBlindedBlock),
+            body: sszBytes ?? getExecutionForkTypes(fork).SignedBlindedBeaconBlock.serialize(signedBlindedBlock),
             headers: {
               [MetaHeader.Version]: fork,
             },
diff --git a/packages/beacon-node/src/api/impl/beacon/blocks/index.ts b/packages/beacon-node/src/api/impl/beacon/blocks/index.ts
index b54e8752a43..685d2212dc9 100644
--- a/packages/beacon-node/src/api/impl/beacon/blocks/index.ts
+++ b/packages/beacon-node/src/api/impl/beacon/blocks/index.ts
@@ -269,7 +269,7 @@ export function getBeaconBlockApi({
     const source = ProducedBlockSource.builder;
     chain.logger.debug("Reconstructing  signedBlockOrContents", {slot, blockRoot, source});
 
-    const signedBlockOrContents = await reconstructBuilderBlockOrContents(chain, signedBlindedBlock);
+    const signedBlockOrContents = await reconstructBuilderBlockOrContents(chain, signedBlindedBlock, context?.sszBytes);
 
     // the full block is published by relay and it's possible that the block is already known to us
     // by gossip
@@ -507,13 +507,14 @@ export function getBeaconBlockApi({
 
 async function reconstructBuilderBlockOrContents(
   chain: ApiModules["chain"],
-  signedBlindedBlock: SignedBlindedBeaconBlock
+  signedBlindedBlock: SignedBlindedBeaconBlock,
+  sszBytes?: Uint8Array | null
 ): Promise<SignedBeaconBlockOrContents> {
   const executionBuilder = chain.executionBuilder;
   if (!executionBuilder) {
     throw Error("executionBuilder required to publish SignedBlindedBeaconBlock");
   }
 
-  const signedBlockOrContents = await executionBuilder.submitBlindedBlock(signedBlindedBlock);
+  const signedBlockOrContents = await executionBuilder.submitBlindedBlock(signedBlindedBlock, sszBytes);
   return signedBlockOrContents;
 }
diff --git a/packages/beacon-node/src/execution/builder/http.ts b/packages/beacon-node/src/execution/builder/http.ts
index 13f797d1c69..fc81e4fa365 100644
--- a/packages/beacon-node/src/execution/builder/http.ts
+++ b/packages/beacon-node/src/execution/builder/http.ts
@@ -149,9 +149,12 @@ export class ExecutionBuilderHttp implements IExecutionBuilder {
     return {header, executionPayloadValue, blobKzgCommitments, executionRequests};
   }
 
-  async submitBlindedBlock(signedBlindedBlock: SignedBlindedBeaconBlock): Promise<SignedBeaconBlockOrContents> {
+  async submitBlindedBlock(
+    signedBlindedBlock: SignedBlindedBeaconBlock,
+    sszBytes?: Uint8Array | null
+  ): Promise<SignedBeaconBlockOrContents> {
     const res = await this.api.submitBlindedBlock(
-      {signedBlindedBlock},
+      {signedBlindedBlock, sszBytes},
       {retries: 2, requestWireFormat: this.sszSupported ? WireFormat.ssz : WireFormat.json}
     );
 
diff --git a/packages/beacon-node/src/execution/builder/interface.ts b/packages/beacon-node/src/execution/builder/interface.ts
index 5a6a4eb82f6..89394dbcfab 100644
--- a/packages/beacon-node/src/execution/builder/interface.ts
+++ b/packages/beacon-node/src/execution/builder/interface.ts
@@ -39,5 +39,8 @@ export interface IExecutionBuilder {
     blobKzgCommitments?: deneb.BlobKzgCommitments;
     executionRequests?: electra.ExecutionRequests;
   }>;
-  submitBlindedBlock(signedBlock: SignedBlindedBeaconBlock): Promise<SignedBeaconBlockOrContents>;
+  submitBlindedBlock(
+    signedBlindedBlock: SignedBlindedBeaconBlock,
+    sszBytes?: Uint8Array | null
+  ): Promise<SignedBeaconBlockOrContents>;
 }