diff --git a/app/common/gristUrls.ts b/app/common/gristUrls.ts
index cdd2b5c3..1f7039f0 100644
--- a/app/common/gristUrls.ts
+++ b/app/common/gristUrls.ts
@@ -185,7 +185,7 @@ export interface OrgUrlInfo {
   orgInPath?: string;     // If /o/{orgInPath} should be used to access the requested org.
 }
 
-export function hostMatchesUrl(host?: string, url?: string) {
+function hostMatchesUrl(host?: string, url?: string) {
   return host !== undefined && url !== undefined && new URL(url).host === host;
 }
 
diff --git a/app/gen-server/lib/DocApiForwarder.ts b/app/gen-server/lib/DocApiForwarder.ts
index 4be608af..e79e2cd7 100644
--- a/app/gen-server/lib/DocApiForwarder.ts
+++ b/app/gen-server/lib/DocApiForwarder.ts
@@ -104,7 +104,7 @@ export class DocApiForwarder {
     url.pathname = removeTrailingSlash(docWorkerUrl.pathname) + url.pathname;
 
     const headers: {[key: string]: string} = {
-      ...getTransitiveHeaders(req),
+      ...getTransitiveHeaders(req, { includeOrigin: true }),
       'Content-Type': req.get('Content-Type') || 'application/json',
     };
     for (const key of ['X-Sort', 'X-Limit']) {
diff --git a/app/server/lib/AppEndpoint.ts b/app/server/lib/AppEndpoint.ts
index a676f5e7..c38f6e0e 100644
--- a/app/server/lib/AppEndpoint.ts
+++ b/app/server/lib/AppEndpoint.ts
@@ -149,7 +149,7 @@ export function attachAppEndpoint(options: AttachOptions): void {
       // TODO docWorkerMain needs to serve app.html, perhaps with correct base-href already set.
       const headers = {
         Accept: 'application/json',
-        ...getTransitiveHeaders(req),
+        ...getTransitiveHeaders(req, { includeOrigin: true }),
       };
       const workerInfo = await getWorker(docWorkerMap, docId, `/${docId}/app.html`, {headers});
       docStatus = workerInfo.docStatus;
diff --git a/app/server/lib/Authorizer.ts b/app/server/lib/Authorizer.ts
index 2ad7d134..b8c85981 100644
--- a/app/server/lib/Authorizer.ts
+++ b/app/server/lib/Authorizer.ts
@@ -677,7 +677,10 @@ export function assertAccess(
  * Pull out headers to pass along to a proxied service.  Focused primarily on
  * authentication.
  */
-export function getTransitiveHeaders(req: Request): {[key: string]: string} {
+export function getTransitiveHeaders(
+  req: Request,
+  { includeOrigin }: { includeOrigin: boolean }
+): {[key: string]: string} {
   const Authorization = req.get('Authorization');
   const Cookie = req.get('Cookie');
   const PermitHeader = req.get('Permit');
@@ -685,8 +688,6 @@ export function getTransitiveHeaders(req: Request): {[key: string]: string} {
   const XRequestedWith = req.get('X-Requested-With');
   const Origin = req.get('Origin');  // Pass along the original Origin since it may
                                      // play a role in granular access control.
-  const Host = req.get('Host');      // Also pass along the original Host, as we need it since
-                                     // the destination compares that with the Origin header.
 
   const result: Record<string, string> = {
     ...(Authorization ? { Authorization } : undefined),
@@ -694,8 +695,7 @@ export function getTransitiveHeaders(req: Request): {[key: string]: string} {
     ...(Organization ? { Organization } : undefined),
     ...(PermitHeader ? { Permit: PermitHeader } : undefined),
     ...(XRequestedWith ? { 'X-Requested-With': XRequestedWith } : undefined),
-    ...(Origin ? { Origin } : undefined),
-    ...(Host ? { Host } : undefined),
+    ...((includeOrigin && Origin) ? { Origin } : undefined),
   };
   const extraHeader = process.env.GRIST_FORWARD_AUTH_HEADER;
   const extraHeaderValue = extraHeader && req.get(extraHeader);
diff --git a/app/server/lib/DocApi.ts b/app/server/lib/DocApi.ts
index 8d33aada..e1dbe3fd 100644
--- a/app/server/lib/DocApi.ts
+++ b/app/server/lib/DocApi.ts
@@ -1102,7 +1102,7 @@ export class DocWorkerApi {
         const result = await fetch(homeUrl, {
           method: 'GET',
           headers: {
-            ...getTransitiveHeaders(req),
+            ...getTransitiveHeaders(req, { includeOrigin: false }),
             'Content-Type': 'application/json',
           }
         });
@@ -1115,7 +1115,7 @@ export class DocWorkerApi {
         await fetch(this._grist.getHomeInternalUrl(`/api/docs/${options.sourceDocId}/flush`), {
           method: 'POST',
           headers: {
-            ...getTransitiveHeaders(req),
+            ...getTransitiveHeaders(req, { includeOrigin: false }),
             'Content-Type': 'application/json',
           }
         });
@@ -1173,7 +1173,7 @@ export class DocWorkerApi {
       const {states} = await this._getStates(docSession, activeDoc);
       const ref = await fetch(this._grist.getHomeInternalUrl(`/api/docs/${req.params.docId2}/states`), {
         headers: {
-          ...getTransitiveHeaders(req),
+          ...getTransitiveHeaders(req, { includeOrigin: false }),
           'Content-Type': 'application/json',
         }
       });
@@ -1202,7 +1202,7 @@ export class DocWorkerApi {
         const url = `/api/docs/${req.params.docId2}/compare?left=${parent.h}`;
         const rightChangesReq = await fetch(this._grist.getHomeInternalUrl(url), {
           headers: {
-            ...getTransitiveHeaders(req),
+            ...getTransitiveHeaders(req, { includeOrigin: false }),
             'Content-Type': 'application/json',
           }
         });
diff --git a/app/server/lib/FlexServer.ts b/app/server/lib/FlexServer.ts
index 6a7af17b..59d8a3e5 100644
--- a/app/server/lib/FlexServer.ts
+++ b/app/server/lib/FlexServer.ts
@@ -2436,7 +2436,7 @@ export class FlexServer implements GristServer {
     const copyDocUrl = this.getHomeInternalUrl('/api/docs');
     const response = await fetch(copyDocUrl, {
       headers: {
-        ...getTransitiveHeaders(req),
+        ...getTransitiveHeaders(req, { includeOrigin: false }),
         'Content-Type': 'application/json',
       },
       method: 'POST',
diff --git a/app/server/lib/uploads.ts b/app/server/lib/uploads.ts
index c2a2eaa1..4c78df30 100644
--- a/app/server/lib/uploads.ts
+++ b/app/server/lib/uploads.ts
@@ -420,7 +420,7 @@ export async function fetchDoc(
   template: boolean
 ): Promise<UploadResult> {
   // Prepare headers that preserve credentials of current user.
-  const headers = getTransitiveHeaders(req);
+  const headers = getTransitiveHeaders(req, { includeOrigin: false });
 
   // Passing the Origin header would serve no purpose here, as we are
   // constructing an internal request to fetch from our own doc worker