diff --git a/packages/vite/src/node/utils.ts b/packages/vite/src/node/utils.ts
index 4cb6931e7317de..c12e429c51529d 100644
--- a/packages/vite/src/node/utils.ts
+++ b/packages/vite/src/node/utils.ts
@@ -79,6 +79,7 @@ export const flattenId = (id: string): string =>
     .replace(/[/:]/g, '_')
     .replace(/\./g, '__')
     .replace(/(\s*>\s*)/g, '___')
+    .replace(/#/g, '____')
 
 export const normalizeId = (id: string): string =>
   id.replace(/(\s*>\s*)/g, ' > ')
diff --git a/playground/resolve/__tests__/resolve.spec.ts b/playground/resolve/__tests__/resolve.spec.ts
index 483c3767833935..65f973e4c85dd3 100644
--- a/playground/resolve/__tests__/resolve.spec.ts
+++ b/playground/resolve/__tests__/resolve.spec.ts
@@ -155,7 +155,7 @@ test('resolve.conditions', async () => {
 
 test('resolve package that contains # in path', async () => {
   expect(await page.textContent('.path-contains-sharp-symbol')).toMatch(
-    '[success]',
+    '[success] true',
   )
 })
 
diff --git a/playground/resolve/index.html b/playground/resolve/index.html
index 5de5ef46289c69..a562e96847548f 100644
--- a/playground/resolve/index.html
+++ b/playground/resolve/index.html
@@ -340,7 +340,9 @@ <h2>resolve package that contains # in path</h2>
   text('.inline-pkg', inlineMsg)
 
   import es5Ext from 'es5-ext'
-  text('.path-contains-sharp-symbol', '[success]')
+  import contains from 'es5-ext/string/#/contains'
+
+  text('.path-contains-sharp-symbol', `[success] ${contains.call('#', '#')}`)
 </script>
 
 <style>