diff --git a/packages/configure/src/utils/authenticated.client.ts b/packages/configure/src/utils/authenticated.client.ts
index 6e08a9ef..e56f825b 100644
--- a/packages/configure/src/utils/authenticated.client.ts
+++ b/packages/configure/src/utils/authenticated.client.ts
@@ -2,8 +2,11 @@ import { Configuration, DefaultApi } from '@flatfile/api'
 // TODO: We will need to make this conditional depending on if it's in the NodeVM or the Browser
 import fetch, { RequestInit } from 'node-fetch'
 
-const FLATFILE_API_URL =
-  process.env.AGENT_INTERNAL_URL || 'http://localhost:3000'
+const FLATFILE_API_URL = process.env.AGENT_INTERNAL_URL
+
+if (FLATFILE_API_URL == null) {
+  throw new Error('AGENT_INTERNAL_URL must be set in the environment')
+}
 
 export class AuthenticatedClient {
   private _api?: DefaultApi
diff --git a/packages/listener/src/events/authenticated.client.ts b/packages/listener/src/events/authenticated.client.ts
index 6d994acc..614f174d 100644
--- a/packages/listener/src/events/authenticated.client.ts
+++ b/packages/listener/src/events/authenticated.client.ts
@@ -7,8 +7,12 @@ export class AuthenticatedClient {
   public _apiUrl?: string
 
   constructor(accessToken?: string, apiUrl?: string) {
-    const FLATFILE_API_URL =
-      CrossEnvConfig.get('AGENT_INTERNAL_URL') || 'http://localhost:3000'
+    const FLATFILE_API_URL = CrossEnvConfig.get('AGENT_INTERNAL_URL')
+
+    if (FLATFILE_API_URL == null) {
+      throw new Error('AGENT_INTERNAL_URL must be set in the environment')
+    }
+
     const bearerToken = CrossEnvConfig.get('FLATFILE_BEARER_TOKEN')
 
     this._accessToken = accessToken || bearerToken || '...'
diff --git a/packages/listener/src/events/event.handler.spec.ts b/packages/listener/src/events/event.handler.spec.ts
index 8eb31205..ce12c47a 100644
--- a/packages/listener/src/events/event.handler.spec.ts
+++ b/packages/listener/src/events/event.handler.spec.ts
@@ -1,8 +1,13 @@
+import { CrossEnvConfig } from '@flatfile/cross-env-config'
 import { EventHandler } from './event.handler'
 
 describe('EventHandler', () => {
   let testFn: jest.Mock
 
+  if (CrossEnvConfig.get('AGENT_INTERNAL_URL') == null) {
+    process.env.AGENT_INTERNAL_URL = 'agent_internal_url'
+  }
+
   beforeEach(() => {
     testFn = jest.fn()
   })
@@ -86,4 +91,19 @@ describe('EventHandler', () => {
       expect(testFn).toHaveBeenCalledTimes(1)
     })
   })
+
+  describe('AGENT_INTERNAL_URL', () => {
+    test('throws error when not set', () => {
+      process.env.AGENT_INTERNAL_URL = undefined
+
+      try {
+        new EventHandler().on('foo', testFn)
+      } catch (e) {
+        expect(e).toBeInstanceOf(Error)
+        expect((e as Error).message).toBe(
+          'AGENT_INTERNAL_URL must be set in the environment'
+        )
+      }
+    })
+  })
 })
diff --git a/packages/listener/src/flatfile.listener.spec.ts b/packages/listener/src/flatfile.listener.spec.ts
index a0e884b1..a301f006 100644
--- a/packages/listener/src/flatfile.listener.spec.ts
+++ b/packages/listener/src/flatfile.listener.spec.ts
@@ -1,8 +1,13 @@
+import { CrossEnvConfig } from '@flatfile/cross-env-config'
 import { FlatfileListener } from './flatfile.listener'
 
 describe('Client', () => {
   let testFn: jest.Mock
 
+  if (CrossEnvConfig.get('AGENT_INTERNAL_URL') == null) {
+    process.env.AGENT_INTERNAL_URL = 'agent_internal_url'
+  }
+
   beforeEach(() => {
     testFn = jest.fn()
   })
@@ -150,4 +155,21 @@ describe('Client', () => {
       expect(testFn).toHaveBeenCalledTimes(3)
     })
   })
+
+  describe('AGENT_INTERNAL_URL', () => {
+    test('throws error when not set', () => {
+      process.env.AGENT_INTERNAL_URL = undefined
+
+      try {
+        FlatfileListener.create((c) => {
+          c.on('foo', () => {})
+        })
+      } catch (e) {
+        expect(e).toBeInstanceOf(Error)
+        expect((e as Error).message).toBe(
+          'AGENT_INTERNAL_URL must be set in the environment'
+        )
+      }
+    })
+  })
 })