diff --git a/lib/util/cache.js b/lib/util/cache.js
index 35c53512b2a..a4cba958bd4 100644
--- a/lib/util/cache.js
+++ b/lib/util/cache.js
@@ -260,19 +260,16 @@ function parseVaryHeader (varyHeader, headers) {
     return headers
   }
 
-  const output = /** @type {Record<string, string | string[]>} */ ({})
+  const output = /** @type {Record<string, string | string[] | null>} */ ({})
 
   const varyingHeaders = typeof varyHeader === 'string'
     ? varyHeader.split(',')
     : varyHeader
+
   for (const header of varyingHeaders) {
     const trimmedHeader = header.trim().toLowerCase()
 
-    if (headers[trimmedHeader]) {
-      output[trimmedHeader] = headers[trimmedHeader]
-    } else {
-      return undefined
-    }
+    output[trimmedHeader] = headers[trimmedHeader] ?? null
   }
 
   return output
diff --git a/test/types/cache-interceptor.test-d.ts b/test/types/cache-interceptor.test-d.ts
index 6fb66955de5..7dcad3c454c 100644
--- a/test/types/cache-interceptor.test-d.ts
+++ b/test/types/cache-interceptor.test-d.ts
@@ -78,6 +78,45 @@ expectNotAssignable<CacheInterceptor.CacheValue>({
   deleteAt: ''
 })
 
+expectAssignable<CacheInterceptor.CacheValue>({
+  statusCode: 200,
+  statusMessage: 'OK',
+  headers: {},
+  vary: {
+    'accept-encoding': null,
+    authorization: 'Bearer token'
+  },
+  cachedAt: 0,
+  staleAt: 0,
+  deleteAt: 0
+})
+
+expectAssignable<CacheInterceptor.CacheValue>({
+  statusCode: 200,
+  statusMessage: 'OK',
+  headers: {},
+  vary: {
+    'accept-encoding': null,
+    authorization: null
+  },
+  cachedAt: 0,
+  staleAt: 0,
+  deleteAt: 0
+})
+
+expectNotAssignable<CacheInterceptor.CacheValue>({
+  statusCode: 200,
+  statusMessage: 'OK',
+  headers: {},
+  vary: {
+    'accept-encoding': true,
+    authorization: 'Bearer token'
+  },
+  cachedAt: 0,
+  staleAt: 0,
+  deleteAt: 0
+})
+
 expectAssignable<CacheInterceptor.MemoryCacheStoreOpts>({})
 expectAssignable<CacheInterceptor.MemoryCacheStoreOpts>({
   maxSize: 0
diff --git a/test/utils/cache.js b/test/utils/cache.js
new file mode 100644
index 00000000000..c9f9cbc8be9
--- /dev/null
+++ b/test/utils/cache.js
@@ -0,0 +1,39 @@
+const { describe, test } = require('node:test')
+const assert = require('node:assert')
+const { parseVaryHeader } = require('../../lib/util/cache.js')
+
+describe('parseVaryHeader', () => {
+  test('handles missing headers with null', () => {
+    const result = parseVaryHeader('Accept-Encoding, Authorization', {})
+    assert.deepStrictEqual(result, {
+      'accept-encoding': null,
+      authorization: null
+    })
+  })
+
+  test('handles mix of present and missing headers', () => {
+    const result = parseVaryHeader('Accept-Encoding, Authorization', {
+      authorization: 'Bearer token'
+    })
+    assert.deepStrictEqual(result, {
+      'accept-encoding': null,
+      authorization: 'Bearer token'
+    })
+  })
+
+  test('handles array input', () => {
+    const result = parseVaryHeader(['Accept-Encoding', 'Authorization'], {
+      'accept-encoding': 'gzip'
+    })
+    assert.deepStrictEqual(result, {
+      'accept-encoding': 'gzip',
+      authorization: null
+    })
+  })
+
+  test('preserves existing * behavior', () => {
+    const headers = { accept: 'text/html' }
+    const result = parseVaryHeader('*', headers)
+    assert.deepStrictEqual(result, headers)
+  })
+})
diff --git a/types/cache-interceptor.d.ts b/types/cache-interceptor.d.ts
index 1713ca7e747..e53be60a611 100644
--- a/types/cache-interceptor.d.ts
+++ b/types/cache-interceptor.d.ts
@@ -70,7 +70,7 @@ declare namespace CacheHandler {
     statusCode: number
     statusMessage: string
     headers: Record<string, string | string[]>
-    vary?: Record<string, string | string[]>
+    vary?: Record<string, string | string[] | null>
     etag?: string
     cacheControlDirectives?: CacheControlDirectives
     cachedAt: number
@@ -88,7 +88,7 @@ declare namespace CacheHandler {
     statusCode: number
     statusMessage: string
     headers: Record<string, string | string[]>
-    vary?: Record<string, string | string[]>
+    vary?: Record<string, string | string[] | null>
     etag?: string
     body?: Readable | Iterable<Buffer> | AsyncIterable<Buffer> | Buffer | Iterable<string> | AsyncIterable<string> | string
     cacheControlDirectives: CacheControlDirectives,