diff --git a/helpers/doesNotNeedPlugin.js b/helpers/doesNotNeedPlugin.js
index a2898f9653..c4f52a7a5b 100644
--- a/helpers/doesNotNeedPlugin.js
+++ b/helpers/doesNotNeedPlugin.js
@@ -1,8 +1,9 @@
 // Checks all the cases for which the plugin should do nothing
-const { redBright } = require('chalk')
+const { redBright, yellowBright } = require('chalk')
 
 const doesSiteUseNextOnNetlify = require('./doesSiteUseNextOnNetlify')
 const isStaticExportProject = require('./isStaticExportProject')
+const usesBuildCommand = require('./usesBuildCommand')
 
 const doesNotNeedPlugin = ({ netlifyConfig, packageJson }) => {
   const { build } = netlifyConfig
@@ -15,6 +16,13 @@ const doesNotNeedPlugin = ({ netlifyConfig, packageJson }) => {
     return true
   }
 
+  if (usesBuildCommand({ build, scripts, command: 'build-storybook' })) {
+    console.log(
+      yellowBright`Site seems to be building a Storybook rather than the Next.js site, so the Essential Next.js plugin will not run.`,
+    )
+    return true
+  }
+
   return isStaticExportProject({ build, scripts }) || doesSiteUseNextOnNetlify({ packageJson })
 }
 
diff --git a/helpers/isStaticExportProject.js b/helpers/isStaticExportProject.js
index f5a1a12d26..ff705297b9 100644
--- a/helpers/isStaticExportProject.js
+++ b/helpers/isStaticExportProject.js
@@ -1,19 +1,12 @@
+const usesBuildCommand = require('./usesBuildCommand')
+
 // Takes 1. Netlify config's build details and
 // 2. the project's package.json scripts to determine if
 // the Next.js app uses static HTML export
 const isStaticExportProject = ({ build, scripts }) => {
   const NEXT_EXPORT_COMMAND = 'next export'
 
-  if (!build.command) return false
-
-  const isSetInNetlifyConfig = build.command.includes(NEXT_EXPORT_COMMAND)
-
-  const isSetInNpmScript = Object.keys(scripts).find((script) => {
-    const scriptValue = scripts[script]
-    return build.command.includes(script) && scriptValue.includes(NEXT_EXPORT_COMMAND)
-  })
-
-  const isStaticExport = isSetInNetlifyConfig || isSetInNpmScript
+  const isStaticExport = usesBuildCommand({ build, scripts, command: NEXT_EXPORT_COMMAND })
 
   if (isStaticExport) {
     console.log(
diff --git a/helpers/usesBuildCommand.js b/helpers/usesBuildCommand.js
new file mode 100644
index 0000000000..e0fe4f1ff4
--- /dev/null
+++ b/helpers/usesBuildCommand.js
@@ -0,0 +1,15 @@
+// Does the build command include this value, either directly or via an npm script?
+const usesBuildCommand = ({ build, scripts, command }) => {
+  if (!build.command) return false
+
+  if (build.command.includes(command)) {
+    return true
+  }
+
+  return Object.entries(scripts).some(
+    // Search for a npm script that is being called by the build command, and includes the searched-for command
+    ([scriptName, scriptValue]) => build.command.includes(scriptName) && scriptValue.includes(command),
+  )
+}
+
+module.exports = usesBuildCommand
diff --git a/index.js b/index.js
index b85fded5c1..9e359dc074 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,4 @@
-const { readdirSync } = require('fs')
+const { readdirSync, existsSync } = require('fs')
 const path = require('path')
 
 const makeDir = require('make-dir')
@@ -71,6 +71,19 @@ module.exports = {
     if (doesNotNeedPlugin({ netlifyConfig, packageJson, failBuild })) {
       return
     }
+    console.log('Detected Next.js site. Copying files...')
+
+    const { distDir } = await getNextConfig(failBuild, nextRoot)
+
+    const dist = path.resolve(nextRoot, distDir)
+    if (!existsSync(dist)) {
+      failBuild(`
+Could not find "${distDir}" after building the site, which indicates that "next build" was not run. 
+Check that your build command includes "next build". If the site is a monorepo, see https://ntl.fyi/next-monorepo 
+for information on configuring the site. If this is not a Next.js site you should remove the Essential Next.js plugin. 
+See https://ntl.fyi/remove-plugin for instructions.
+      `)
+    }
 
     console.log(`** Running Next on Netlify package **`)
 
@@ -87,7 +100,7 @@ module.exports = {
       utils.status.show({
         title: 'Essential Next.js Build Plugin did not run',
         summary: netlifyConfig.build.command
-          ? 'The site either uses static export, or manually runs next-on-netlify'
+          ? 'The site either uses static export, manually runs next-on-netlify, or is not a Next.js site'
           : 'The site config does not specify a build command',
       })
       return
diff --git a/test/index.js b/test/index.js
index b857036dd8..c124088863 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,3 +1,5 @@
+/* eslint-disable max-lines */
+/* eslint-disable max-lines-per-function */
 const path = require('path')
 const process = require('process')
 
@@ -156,6 +158,33 @@ describe('preBuild()', () => {
     expect(process.env.NEXT_PRIVATE_TARGET).toBeUndefined()
   })
 
+  test('do nothing if build command includes "build-storybook"', async () => {
+    await plugin.onPreBuild({
+      netlifyConfig,
+      packageJson: { ...DUMMY_PACKAGE_JSON, scripts: { build: 'build-storybook' } },
+      utils,
+    })
+    expect(process.env.NEXT_PRIVATE_TARGET).toBeUndefined()
+  })
+
+  test('do nothing if build command calls a script that includes "build-storybook"', async () => {
+    await plugin.onPreBuild({
+      netlifyConfig: { build: { command: 'npm run storybook' } },
+      packageJson: { ...DUMMY_PACKAGE_JSON, scripts: { storybook: 'build-storybook' } },
+      utils,
+    })
+    expect(process.env.NEXT_PRIVATE_TARGET).toBeUndefined()
+  })
+
+  test('run plugin if app has build-storybook in an unused script', async () => {
+    await plugin.onPreBuild({
+      netlifyConfig,
+      packageJson: { ...DUMMY_PACKAGE_JSON, scripts: { storybook: 'build-storybook' } },
+      utils,
+    })
+    expect(process.env.NEXT_PRIVATE_TARGET).toBe('serverless')
+  })
+
   test('fail build if the app has no package.json', async () => {
     await expect(
       plugin.onPreBuild({
@@ -289,3 +318,6 @@ describe('onPostBuild', () => {
     expect(path.normalize(manifestPath.digests[0])).toBe(path.normalize('build/build-manifest.json'))
   })
 })
+
+/* eslint-enable max-lines */
+/* eslint-enable max-lines-per-function */