diff --git a/packages/preview-process/src/parts/HttpHeader/HttpHeader.ts b/packages/preview-process/src/parts/HttpHeader/HttpHeader.ts
index 6edf7f4f..066cc2ac 100644
--- a/packages/preview-process/src/parts/HttpHeader/HttpHeader.ts
+++ b/packages/preview-process/src/parts/HttpHeader/HttpHeader.ts
@@ -8,5 +8,5 @@ export const ContentType = 'Content-Type'
 export const CrossOriginEmbedderPolicy = 'Cross-Origin-Embedder-Policy'
 export const CrossOriginOpenerPolicy = 'Cross-Origin-Opener-Policy'
 export const CrossOriginResourcePolicy = 'Cross-Origin-Resource-Policy'
-export const Etag = 'Etag'
+export const Etag = 'ETag'
 export const IfNotMatch = 'if-none-match'
diff --git a/packages/preview-process/src/parts/ToTitleCase/ToTitleCase.ts b/packages/preview-process/src/parts/ToTitleCase/ToTitleCase.ts
index 282c5deb..59cd0826 100644
--- a/packages/preview-process/src/parts/ToTitleCase/ToTitleCase.ts
+++ b/packages/preview-process/src/parts/ToTitleCase/ToTitleCase.ts
@@ -1,4 +1,12 @@
+const SPECIAL_CASES: Record<string, string> = {
+  etag: 'ETag',
+}
+
 export const toTitleCase = (key: string): string => {
+  const lowerKey = key.toLowerCase()
+  if (SPECIAL_CASES[lowerKey]) {
+    return SPECIAL_CASES[lowerKey]
+  }
   return key
     .split('-')
     .map((part) => part.charAt(0).toUpperCase() + part.slice(1).toLowerCase())
diff --git a/packages/preview-process/test/SerializeHeaders.test.ts b/packages/preview-process/test/SerializeHeaders.test.ts
index e3ab64c7..a394d787 100644
--- a/packages/preview-process/test/SerializeHeaders.test.ts
+++ b/packages/preview-process/test/SerializeHeaders.test.ts
@@ -21,7 +21,7 @@ test('serializeHeaders - multiple headers', () => {
   headers.set('Cross-Origin-Resource-Policy', 'same-origin')
   expect(SerializeHeaders.serializeHeaders(headers)).toEqual({
     'Content-Type': 'text/plain',
-    Etag: '"123"',
+    ETag: '"123"',
     'Cross-Origin-Resource-Policy': 'same-origin',
   })
 })
diff --git a/packages/preview-process/test/SerializeResponse.test.ts b/packages/preview-process/test/SerializeResponse.test.ts
index e3a16c97..0f7a5fe3 100644
--- a/packages/preview-process/test/SerializeResponse.test.ts
+++ b/packages/preview-process/test/SerializeResponse.test.ts
@@ -55,7 +55,7 @@ test('serializeResponse - with no content', async () => {
     init: {
       status: 304,
       headers: {
-        Etag: '"123"',
+        ETag: '"123"',
       },
     },
   })
diff --git a/packages/preview-process/test/ToTitleCase.test.ts b/packages/preview-process/test/ToTitleCase.test.ts
index 19022788..d621e3fd 100644
--- a/packages/preview-process/test/ToTitleCase.test.ts
+++ b/packages/preview-process/test/ToTitleCase.test.ts
@@ -24,3 +24,13 @@ test('toTitleCase - mixed case', () => {
 test('toTitleCase - multiple hyphens', () => {
   expect(ToTitleCase.toTitleCase('cross-origin-resource-policy')).toBe('Cross-Origin-Resource-Policy')
 })
+
+test('toTitleCase - etag special case', () => {
+  expect(ToTitleCase.toTitleCase('etag')).toBe('ETag')
+})
+
+test('toTitleCase - etag special case with different casing', () => {
+  expect(ToTitleCase.toTitleCase('ETAG')).toBe('ETag')
+  expect(ToTitleCase.toTitleCase('ETag')).toBe('ETag')
+  expect(ToTitleCase.toTitleCase('etAG')).toBe('ETag')
+})