diff --git a/src/rpc/cfx.js b/src/rpc/cfx.js
index 2af3dbf..e27930a 100644
--- a/src/rpc/cfx.js
+++ b/src/rpc/cfx.js
@@ -8,7 +8,6 @@ const { decodeCfxAddress, ADDRESS_TYPES } = require('../util/address');
 const PendingTransaction = require('../subscribe/PendingTransaction');
 const Contract = require('../contract');
 const RPCTypes = require('./types/index');
-const { fastFormatEpochReceipts, fastFormatBlock } = require('./types/fastFormatter');
 
 /**
  * @typedef { import('../Transaction').TransactionMeta } TransactionMeta
@@ -189,12 +188,11 @@ class CFX extends RPCMethodFactory {
       {
         method: 'cfx_getBlockByHashWithPivotAssumption',
         requestFormatters: [
-          v => v, // format.blockHash,
-          v => v, // blockHash,
+          format.blockHash,
+          format.blockHash,
           format.epochNumber,
         ],
-        // responseFormatter: cfxFormat.block,
-        responseFormatter: fastFormatBlock,
+        responseFormatter: cfxFormat.block,
       },
       {
         method: 'cfx_getConfirmationRiskByHash',
@@ -605,8 +603,7 @@ class CFX extends RPCMethodFactory {
         ...extra,
       ],
     });
-    // return cfxFormat.epochReceipts(result);
-    return fastFormatEpochReceipts(result);
+    return cfxFormat.epochReceipts(result);
   }
 
   /**
diff --git a/src/rpc/index.js b/src/rpc/index.js
index 00e9319..ccb356c 100644
--- a/src/rpc/index.js
+++ b/src/rpc/index.js
@@ -1,4 +1,5 @@
 const format = require('../util/format');
+const { rpcPatch } = require('./rpcPatch');
 
 class RPCMethodFactory {
   constructor(conflux, methods = []) {
@@ -8,6 +9,7 @@ class RPCMethodFactory {
 
   addMethods(methods) {
     for (const methodMeta of methods) {
+      rpcPatch(methodMeta);
       const method = methodMeta.method.split('_')[1];
       this[method] = this.createRPCMethod(methodMeta);
       // create method alias
diff --git a/src/rpc/rpcPatch.js b/src/rpc/rpcPatch.js
new file mode 100644
index 0000000..98a8596
--- /dev/null
+++ b/src/rpc/rpcPatch.js
@@ -0,0 +1,19 @@
+/**
+ * Give a chance to change the RPC behavior.
+ * For example, you may want to use a different responseFormatter for traceBlock.
+ * @param rpcDef
+ */
+
+// eslint-disable-next-line no-unused-vars
+function emptyPatchRPCMethod(rpcDef) {
+  // const { method, requestFormatters, responseFormatter } = rpcDef;
+}
+
+let rpcPatch = emptyPatchRPCMethod;
+
+// set it before initializing a new Conflux instance.
+function setPRCMethodPatch(fn) {
+  rpcPatch = fn;
+}
+
+module.exports = { rpcPatch, setPRCMethodPatch };
diff --git a/src/rpc/trace.js b/src/rpc/trace.js
index 1fce2e7..b3d8021 100644
--- a/src/rpc/trace.js
+++ b/src/rpc/trace.js
@@ -1,6 +1,5 @@
 const RPCMethodFactory = require('./index');
 const format = require('../util/format');
-const { fastFormatBlockTraces } = require('./types/fastFormatter');
 
 /**
  * @typedef {Object} ActionCall
@@ -175,11 +174,10 @@ class Trace extends RPCMethodFactory {
       {
         method: 'trace_block',
         alias: 'traceBlock',
-        // requestFormatters: [
-        //   format.blockHash,
-        // ],
-        // responseFormatter: format.blockTraces,
-        responseFormatter: fastFormatBlockTraces,
+        requestFormatters: [
+          format.blockHash,
+        ],
+        responseFormatter: format.blockTraces,
       },
       {
         method: 'trace_transaction',
diff --git a/src/rpc/types/fastFormatter.js b/src/rpc/types/fastFormatter.js
index 86a7e6d..ebf8e93 100644
--- a/src/rpc/types/fastFormatter.js
+++ b/src/rpc/types/fastFormatter.js
@@ -1,3 +1,5 @@
+const cfxFormat = require('./formatter');
+
 function maybeBigInt(v, prop) {
   if (v[prop] === undefined) {
     return;
@@ -88,4 +90,25 @@ function fastFormatBlock(v) {
   return v;
 }
 
-module.exports = { fastFormatBlockTraces, fastFormatEpochReceipts, fastFormatBlock };
+const nothing = v => v;
+// use setPRCMethodPatch(useFastFormat) to enable it.
+function useFastFormat(rpcDef) {
+  cfxFormat.epochReceipts = fastFormatEpochReceipts;
+  cfxFormat.hex64 = nothing;
+  const { method } = rpcDef;
+  switch (method) {
+    case 'cfx_getBlockByHashWithPivotAssumption':
+      rpcDef.requestFormatters[0] = undefined;
+      rpcDef.requestFormatters[1] = undefined;
+      rpcDef.responseFormatter = fastFormatBlock;
+      break;
+    case 'trace_block':
+      rpcDef.requestFormatters = undefined;
+      rpcDef.responseFormatter = fastFormatBlockTraces;
+      break;
+    default:
+      break;
+  }
+}
+
+module.exports = { fastFormatBlockTraces, fastFormatEpochReceipts, fastFormatBlock, useFastFormat };