diff --git a/src/storage.ts b/src/storage.ts
index 3201fdaca..c2e0ce027 100644
--- a/src/storage.ts
+++ b/src/storage.ts
@@ -396,6 +396,7 @@ export class Storage extends Service {
     let apiEndpoint = 'https://storage.googleapis.com';
     let customEndpoint = false;
 
+    // Note: EMULATOR_HOST is an experimental configuration variable. Use apiEndpoint instead.
     const EMULATOR_HOST = process.env.STORAGE_EMULATOR_HOST;
     if (typeof EMULATOR_HOST === 'string') {
       apiEndpoint = Storage.sanitizeEndpoint(EMULATOR_HOST);
@@ -409,6 +410,7 @@ export class Storage extends Service {
 
     options = Object.assign({}, options, {apiEndpoint});
 
+    // Note: EMULATOR_HOST is an experimental configuration variable. Use apiEndpoint instead.
     const baseUrl = EMULATOR_HOST || `${options.apiEndpoint}/storage/v1`;
 
     const config = {
diff --git a/test/index.ts b/test/index.ts
index 171098ac8..2b9a007f9 100644
--- a/test/index.ts
+++ b/test/index.ts
@@ -228,6 +228,7 @@ describe('Storage', () => {
     });
 
     describe('STORAGE_EMULATOR_HOST', () => {
+      // Note: EMULATOR_HOST is an experimental configuration variable. Use apiEndpoint instead.
       const EMULATOR_HOST = 'https://internal.benchmark.com/path';
       before(() => {
         process.env.STORAGE_EMULATOR_HOST = EMULATOR_HOST;