diff --git a/src/lib/waku_relay/index.spec.ts b/src/lib/waku_relay/index.spec.ts
index ac83e30dfb..2b27b16ed3 100644
--- a/src/lib/waku_relay/index.spec.ts
+++ b/src/lib/waku_relay/index.spec.ts
@@ -12,7 +12,7 @@ import { RelayCodec, RelayDefaultTopic } from './index';
 
 describe('Waku Relay', () => {
   afterEach(function () {
-    if (this.currentTest!.state === 'failed') {
+    if (this.currentTest?.state === 'failed') {
       console.log(`Test failed, log file name is ${makeLogFileName(this)}`);
     }
   });
@@ -41,15 +41,13 @@ describe('Waku Relay', () => {
 
     await Promise.all([
       new Promise((resolve) =>
-        waku1.libp2p.pubsub.once(
-          'pubsub:subscription-change',
-          (...args: any[]) => resolve(args)
+        waku1.libp2p.pubsub.once('pubsub:subscription-change', () =>
+          resolve(null)
         )
       ),
       new Promise((resolve) =>
-        waku2.libp2p.pubsub.once(
-          'pubsub:subscription-change',
-          (...args: any[]) => resolve(args)
+        waku2.libp2p.pubsub.once('pubsub:subscription-change', () =>
+          resolve(null)
         )
       ),
     ]);
@@ -173,7 +171,7 @@ describe('Waku Relay', () => {
         this.timeout(10_000);
         waku = await Waku.create({ staticNoiseKey: NOISE_KEY_1 });
 
-        nimWaku = new NimWaku(this.test!.ctx!.currentTest!.title);
+        nimWaku = new NimWaku(this.test?.ctx?.currentTest?.title + '');
         await nimWaku.start();
 
         await waku.dial(await nimWaku.getMultiaddrWithId());
@@ -252,7 +250,7 @@ describe('Waku Relay', () => {
           Waku.create({ staticNoiseKey: NOISE_KEY_2 }),
         ]);
 
-        nimWaku = new NimWaku(this.test!.ctx!.currentTest!.title);
+        nimWaku = new NimWaku(this.test?.ctx?.currentTest?.title + '');
         await nimWaku.start();
 
         const nimWakuMultiaddr = await nimWaku.getMultiaddrWithId();
@@ -315,10 +313,9 @@ describe('Waku Relay', () => {
   });
 });
 
-function waitForNextData(pubsub: Pubsub): Promise<WakuMessage> {
-  return new Promise((resolve) => {
+async function waitForNextData(pubsub: Pubsub): Promise<WakuMessage> {
+  const msg = (await new Promise((resolve) => {
     pubsub.once(RelayDefaultTopic, resolve);
-  }).then((msg: any) => {
-    return WakuMessage.decode(msg.data);
-  });
+  })) as Pubsub.InMessage;
+  return WakuMessage.decode(msg.data);
 }
diff --git a/src/lib/waku_relay/index.ts b/src/lib/waku_relay/index.ts
index 286aa874f8..018ca5fe20 100644
--- a/src/lib/waku_relay/index.ts
+++ b/src/lib/waku_relay/index.ts
@@ -94,7 +94,7 @@ export class WakuRelayPubsub extends Gossipsub {
       );
       this.mesh.set(topic, peers);
     }
-    this.mesh.get(topic)!.forEach((id) => {
+    this.mesh.get(topic)?.forEach((id) => {
       this.log('JOIN: Add mesh link to %s in %s', id, topic);
       this._sendGraft(id, topic);
     });
@@ -156,7 +156,7 @@ export class WakuRelayPubsub extends Gossipsub {
         this.lastpub.set(topic, this._now());
       }
 
-      meshPeers!.forEach((peer) => {
+      meshPeers?.forEach((peer) => {
         toSend.add(peer);
       });
     });
diff --git a/src/lib/waku_relay/relay_heartbeat.ts b/src/lib/waku_relay/relay_heartbeat.ts
index 7d418e945e..0dc6995e54 100644
--- a/src/lib/waku_relay/relay_heartbeat.ts
+++ b/src/lib/waku_relay/relay_heartbeat.ts
@@ -23,7 +23,7 @@ export class RelayHeartbeat extends Heartbeat {
 
     const timeout = setTimeout(() => {
       heartbeat();
-      this._heartbeatTimer!.runPeriodically(
+      this._heartbeatTimer?.runPeriodically(
         heartbeat,
         constants.RelayHeartbeatInterval
       );
@@ -36,7 +36,7 @@ export class RelayHeartbeat extends Heartbeat {
       },
       cancel: () => {
         clearTimeout(timeout);
-        clearInterval(this._heartbeatTimer!._intervalId as NodeJS.Timeout);
+        clearInterval(this._heartbeatTimer?._intervalId as NodeJS.Timeout);
       },
     };
   }
@@ -323,7 +323,7 @@ export class RelayHeartbeat extends Heartbeat {
       const topicPeers = this.gossipsub.topics.get(topic);
       fanoutPeers.forEach((id) => {
         if (
-          !topicPeers!.has(id) ||
+          !topicPeers?.has(id) ||
           getScore(id) <
             this.gossipsub._options.scoreThresholds.publishThreshold
         ) {
diff --git a/src/test_utils/log_file.ts b/src/test_utils/log_file.ts
index 74dbae5111..f15f8c4d8d 100644
--- a/src/test_utils/log_file.ts
+++ b/src/test_utils/log_file.ts
@@ -41,9 +41,9 @@ function clean(str: string): string {
 }
 
 export function makeLogFileName(ctx: Context): string {
-  const unitTest = ctx!.currentTest ? ctx!.currentTest : ctx.test;
+  const unitTest = ctx?.currentTest ? ctx!.currentTest : ctx.test;
   let name = clean(unitTest!.title);
-  let suite = unitTest!.parent;
+  let suite = unitTest?.parent;
 
   while (suite && suite.title) {
     name = clean(suite.title) + '_' + name;
diff --git a/src/test_utils/nim_waku.ts b/src/test_utils/nim_waku.ts
index 9b70b11201..61581c1702 100644
--- a/src/test_utils/nim_waku.ts
+++ b/src/test_utils/nim_waku.ts
@@ -213,7 +213,10 @@ export class NimWaku {
     return `http://localhost:${port}/`;
   }
 
-  private async rpcCall(method: string, params: any[]) {
+  private async rpcCall(
+    method: string,
+    params: Array<string | number | unknown>
+  ) {
     const res = await axios.post(
       this.rpcUrl,
       {