diff --git a/packages/google-cloud-videointelligence/.eslintrc.yml b/packages/google-cloud-videointelligence/.eslintrc.yml
index 65f1dce6c0c..73eeec27612 100644
--- a/packages/google-cloud-videointelligence/.eslintrc.yml
+++ b/packages/google-cloud-videointelligence/.eslintrc.yml
@@ -12,3 +12,4 @@ rules:
   eqeqeq: error
   no-warning-comments: warn
   no-var: error
+  prefer-const: error
diff --git a/packages/google-cloud-videointelligence/smoke-test/video_intelligence_service_smoke_test.js b/packages/google-cloud-videointelligence/smoke-test/video_intelligence_service_smoke_test.js
index 443f0b35faf..82c2d8e034f 100644
--- a/packages/google-cloud-videointelligence/smoke-test/video_intelligence_service_smoke_test.js
+++ b/packages/google-cloud-videointelligence/smoke-test/video_intelligence_service_smoke_test.js
@@ -15,5 +15,5 @@
 'use strict';
 
 describe('VideoIntelligenceServiceSmokeTest', () => {
-  $unhandledCase: LongRunningOptionalArrayMethod$
+  LongRunningOptionalArrayMethod$;
 });
diff --git a/packages/google-cloud-videointelligence/src/v1/video_intelligence_service_client.js b/packages/google-cloud-videointelligence/src/v1/video_intelligence_service_client.js
index 6ed0c6467e6..1b94364716c 100644
--- a/packages/google-cloud-videointelligence/src/v1/video_intelligence_service_client.js
+++ b/packages/google-cloud-videointelligence/src/v1/video_intelligence_service_client.js
@@ -154,7 +154,7 @@ class VideoIntelligenceServiceClient {
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
     const videoIntelligenceServiceStubMethods = ['annotateVideo'];
-    for (let methodName of videoIntelligenceServiceStubMethods) {
+    for (const methodName of videoIntelligenceServiceStubMethods) {
       this._innerApiCalls[methodName] = gax.createApiCall(
         videoIntelligenceServiceStub.then(
           stub =>
diff --git a/packages/google-cloud-videointelligence/src/v1beta1/video_intelligence_service_client.js b/packages/google-cloud-videointelligence/src/v1beta1/video_intelligence_service_client.js
index 90327fc9706..c4d1955b3aa 100644
--- a/packages/google-cloud-videointelligence/src/v1beta1/video_intelligence_service_client.js
+++ b/packages/google-cloud-videointelligence/src/v1beta1/video_intelligence_service_client.js
@@ -154,7 +154,7 @@ class VideoIntelligenceServiceClient {
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
     const videoIntelligenceServiceStubMethods = ['annotateVideo'];
-    for (let methodName of videoIntelligenceServiceStubMethods) {
+    for (const methodName of videoIntelligenceServiceStubMethods) {
       this._innerApiCalls[methodName] = gax.createApiCall(
         videoIntelligenceServiceStub.then(
           stub =>
diff --git a/packages/google-cloud-videointelligence/src/v1beta2/video_intelligence_service_client.js b/packages/google-cloud-videointelligence/src/v1beta2/video_intelligence_service_client.js
index 6b73c09e508..06e598197f2 100644
--- a/packages/google-cloud-videointelligence/src/v1beta2/video_intelligence_service_client.js
+++ b/packages/google-cloud-videointelligence/src/v1beta2/video_intelligence_service_client.js
@@ -154,7 +154,7 @@ class VideoIntelligenceServiceClient {
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
     const videoIntelligenceServiceStubMethods = ['annotateVideo'];
-    for (let methodName of videoIntelligenceServiceStubMethods) {
+    for (const methodName of videoIntelligenceServiceStubMethods) {
       this._innerApiCalls[methodName] = gax.createApiCall(
         videoIntelligenceServiceStub.then(
           stub =>
diff --git a/packages/google-cloud-videointelligence/src/v1p1beta1/video_intelligence_service_client.js b/packages/google-cloud-videointelligence/src/v1p1beta1/video_intelligence_service_client.js
index 81231d06fb6..e89e18fd2f1 100644
--- a/packages/google-cloud-videointelligence/src/v1p1beta1/video_intelligence_service_client.js
+++ b/packages/google-cloud-videointelligence/src/v1p1beta1/video_intelligence_service_client.js
@@ -154,7 +154,7 @@ class VideoIntelligenceServiceClient {
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
     const videoIntelligenceServiceStubMethods = ['annotateVideo'];
-    for (let methodName of videoIntelligenceServiceStubMethods) {
+    for (const methodName of videoIntelligenceServiceStubMethods) {
       this._innerApiCalls[methodName] = gax.createApiCall(
         videoIntelligenceServiceStub.then(
           stub =>
diff --git a/packages/google-cloud-videointelligence/src/v1p2beta1/video_intelligence_service_client.js b/packages/google-cloud-videointelligence/src/v1p2beta1/video_intelligence_service_client.js
index a5a766cfda1..211e5255cee 100644
--- a/packages/google-cloud-videointelligence/src/v1p2beta1/video_intelligence_service_client.js
+++ b/packages/google-cloud-videointelligence/src/v1p2beta1/video_intelligence_service_client.js
@@ -154,7 +154,7 @@ class VideoIntelligenceServiceClient {
     // Iterate over each of the methods that the service provides
     // and create an API call method for each.
     const videoIntelligenceServiceStubMethods = ['annotateVideo'];
-    for (let methodName of videoIntelligenceServiceStubMethods) {
+    for (const methodName of videoIntelligenceServiceStubMethods) {
       this._innerApiCalls[methodName] = gax.createApiCall(
         videoIntelligenceServiceStub.then(
           stub =>
diff --git a/packages/google-cloud-videointelligence/system-test/video_intelligence_service_smoke_test.js b/packages/google-cloud-videointelligence/system-test/video_intelligence_service_smoke_test.js
index 4803fddb46b..77af73a780f 100644
--- a/packages/google-cloud-videointelligence/system-test/video_intelligence_service_smoke_test.js
+++ b/packages/google-cloud-videointelligence/system-test/video_intelligence_service_smoke_test.js
@@ -18,16 +18,16 @@ describe('VideoIntelligenceServiceSmokeTest', () => {
   it('successfully makes a call to the service', done => {
     const videoIntelligence = require('../src');
 
-    let client = new videoIntelligence.v1p1beta1.VideoIntelligenceServiceClient(
+    const client = new videoIntelligence.v1p1beta1.VideoIntelligenceServiceClient(
       {
         // optional auth parameters.
       }
     );
 
-    let inputUri = 'gs://demomaker/cat.mp4';
-    let featuresElement = 'LABEL_DETECTION';
-    let features = [featuresElement];
-    let request = {
+    const inputUri = 'gs://demomaker/cat.mp4';
+    const featuresElement = 'LABEL_DETECTION';
+    const features = [featuresElement];
+    const request = {
       inputUri: inputUri,
       features: features,
     };
@@ -36,8 +36,8 @@ describe('VideoIntelligenceServiceSmokeTest', () => {
     client
       .annotateVideo(request)
       .then(responses => {
-        let operation = responses[0];
-        let initialApiResponse = responses[1];
+        const operation = responses[0];
+        const initialApiResponse = responses[1];
         console.log(operation);
         console.log(initialApiResponse);
 
@@ -46,13 +46,13 @@ describe('VideoIntelligenceServiceSmokeTest', () => {
       })
       .then(responses => {
         // The final result of the operation.
-        let result = responses[0];
+        const result = responses[0];
 
         // The metadata value of the completed operation.
-        let metadata = responses[1];
+        const metadata = responses[1];
 
         // The response of the api call returning the complete operation.
-        let finalApiResponse = responses[2];
+        const finalApiResponse = responses[2];
 
         console.log(result);
         console.log(metadata);
@@ -65,16 +65,16 @@ describe('VideoIntelligenceServiceSmokeTest', () => {
   it('successfully makes a call to the service', done => {
     const videoIntelligence = require('../src');
 
-    let client = new videoIntelligence.v1p1beta1.VideoIntelligenceServiceClient(
+    const client = new videoIntelligence.v1p1beta1.VideoIntelligenceServiceClient(
       {
         // optional auth parameters.
       }
     );
 
-    let inputUri = 'gs://demomaker/cat.mp4';
-    let featuresElement = 'LABEL_DETECTION';
-    let features = [featuresElement];
-    let request = {
+    const inputUri = 'gs://demomaker/cat.mp4';
+    const featuresElement = 'LABEL_DETECTION';
+    const features = [featuresElement];
+    const request = {
       inputUri: inputUri,
       features: features,
     };
@@ -83,8 +83,8 @@ describe('VideoIntelligenceServiceSmokeTest', () => {
     client
       .annotateVideo(request)
       .then(responses => {
-        let operation = responses[0];
-        let initialApiResponse = responses[1];
+        const operation = responses[0];
+        const initialApiResponse = responses[1];
 
         // Adding a listener for the "complete" event starts polling for the
         // completion of the operation.