diff --git a/packages/sdk/test/test-utils/FakeJsonRpcServer.ts b/packages/sdk/test/test-utils/FakeJsonRpcServer.ts
index 61d74025fe..1f452fbf41 100644
--- a/packages/sdk/test/test-utils/FakeJsonRpcServer.ts
+++ b/packages/sdk/test/test-utils/FakeJsonRpcServer.ts
@@ -1,10 +1,11 @@
-import { AbiCoder, keccak256, toUtf8Bytes } from 'ethers'
+import { AbiCoder, id } from 'ethers'
 import { once } from 'events'
 import express, { Request, Response } from 'express'
 import { Server } from 'http'
 import { intersection, isArray } from 'lodash'
 import { AddressInfo } from 'net'
 import { promisify } from 'util'
+import { formEthereumFunctionSelector, parseEthereumFunctionSelectorFromCallData } from './utils'
 
 export const CHAIN_ID = 5555
 const BLOCK_NUMBER = 123
@@ -14,12 +15,6 @@ const toHex = (val: number) => {
     return '0x' + val.toString(16)
 }
 
-const getLabelHash = (methodSignature: string) => keccak256(toUtf8Bytes(methodSignature))
-
-const getContractMethodHash = (methodSignature: string) => getLabelHash(methodSignature).substring(2, 10)
-
-const getEventTopicHash = (eventSignature: string) => getLabelHash(eventSignature)
-
 export interface JsonRpcRequest {
     id: string
     method: string
@@ -88,17 +83,17 @@ export class FakeJsonRpcServer {
             return toHex(BLOCK_NUMBER)
         } else if (request.method === 'eth_call') {
             const data: string = request.params[0].data
-            const contractMethodHash = data.substring(2, 10)
-            if (contractMethodHash === getContractMethodHash('getPermissionsForUserId(string,bytes)')) {
+            const functionSelector = parseEthereumFunctionSelectorFromCallData(data)
+            if (functionSelector === formEthereumFunctionSelector('getPermissionsForUserId(string,bytes)')) {
                 // PermissionStructOutput: { canEdit: false, canDelete: false, publishExpiration: 0n, subscribeExpiration: 0n, canGrant: false }
                 return '0x' + '0'.repeat(320)
             } else {
-                throw new Error(`Unknown contract method: ${contractMethodHash}, request: ${JSON.stringify(request)}`)
+                throw new Error(`Unknown contract method: ${functionSelector}, request: ${JSON.stringify(request)}`)
             }
         } else if (request.method === 'eth_getLogs') {
             const topics = request.params[0].topics
-            const topicHash = getEventTopicHash('StreamCreated(string,string)')
-            if ((topics.length !== 1) || (topics[0] !== topicHash)) {
+            const topicId = id('StreamCreated(string,string)')
+            if ((topics.length !== 1) || (topics[0] !== topicId)) {
                 throw new Error('Not implemented')
             }
             if (request.params[0].toBlock !== 'latest') {
@@ -109,7 +104,7 @@ export class FakeJsonRpcServer {
                 const data = new AbiCoder().encode(['string', 'string'], [EVENT_STREAM_ID, JSON.stringify({ partitions: 1 })])
                 return [{
                     address: request.params[0].address,
-                    topics: [topicHash],
+                    topics: [topicId],
                     data,
                     blockNumber: toHex(BLOCK_NUMBER),
                     transactionHash: '0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef',
diff --git a/packages/sdk/test/test-utils/utils.ts b/packages/sdk/test/test-utils/utils.ts
index 9e40e6031a..8b64fca26d 100644
--- a/packages/sdk/test/test-utils/utils.ts
+++ b/packages/sdk/test/test-utils/utils.ts
@@ -5,16 +5,16 @@ import {
     DEFAULT_PARTITION_COUNT,
     Logger,
     MAX_PARTITION_COUNT,
+    merge,
     StreamPartID,
     StreamPartIDUtils,
+    until,
     UserID,
-    merge,
     utf8ToBinary,
-    wait,
-    until
+    wait
 } from '@streamr/utils'
 import crypto from 'crypto'
-import { Wallet } from 'ethers'
+import { id, Wallet } from 'ethers'
 import { once } from 'events'
 import express, { Request, Response } from 'express'
 import { mock } from 'jest-mock-extended'
@@ -318,3 +318,13 @@ export const readUtf8ExampleIndirectly = async (): Promise<string> => {
         })
     })
 }
+
+const ETHEREUM_FUNCTION_SELECTOR_LENGTH = 10  // 0x + 4 bytes
+
+export const formEthereumFunctionSelector = (methodSignature: string): string => {
+    return id(methodSignature).substring(0, ETHEREUM_FUNCTION_SELECTOR_LENGTH)
+}
+
+export const parseEthereumFunctionSelectorFromCallData = (data: string): string => {
+    return data.substring(0, ETHEREUM_FUNCTION_SELECTOR_LENGTH)
+}