diff --git a/app/server/lib/DocApi.ts b/app/server/lib/DocApi.ts
index d6ff0702ff..35e6ec6ac0 100644
--- a/app/server/lib/DocApi.ts
+++ b/app/server/lib/DocApi.ts
@@ -530,11 +530,11 @@ export class DocWorkerApi {
     }));
 
     // Returns the status of any current / pending attachment transfers
-    this._app.get('/api/docs/:docId/attachments/transferStatus', isOwner, withDoc(async (activeDoc, req, res) => {
+    this._app.get('/api/docs/:docId/attachments/transferStatus', canView, withDoc(async (activeDoc, req, res) => {
       res.json(await activeDoc.attachmentTransferStatus());
     }));
 
-    this._app.get('/api/docs/:docId/attachments/store', isOwner,
+    this._app.get('/api/docs/:docId/attachments/store', canView,
       withDoc(async (activeDoc, req, res) => {
         const storeId = await activeDoc.getAttachmentStore();
         res.json({
diff --git a/app/server/lib/uploads.ts b/app/server/lib/uploads.ts
index 08c3585207..1f187459dc 100644
--- a/app/server/lib/uploads.ts
+++ b/app/server/lib/uploads.ts
@@ -1,7 +1,7 @@
 import {ApiError} from 'app/common/ApiError';
 import {InactivityTimer} from 'app/common/InactivityTimer';
 import {FetchUrlOptions, FileUploadResult, UPLOAD_URL_PATH, UploadResult} from 'app/common/uploads';
-import {getUrlFromPrefix} from 'app/common/UserAPI';
+import {DocAttachmentsLocation, getUrlFromPrefix} from 'app/common/UserAPI';
 import {getAuthorizedUserId, getTransitiveHeaders, getUserId, isSingleUserMode,
         RequestWithLogin} from 'app/server/lib/Authorizer';
 import {expressWrap} from 'app/server/lib/expressWrap';
@@ -426,9 +426,31 @@ export async function fetchDoc(
   // The backend needs to be well configured for this to work.
   const { selfPrefix, docWorker } = await getDocWorkerInfoOrSelfPrefix(docId, docWorkerMap, server.getTag());
   const docWorkerUrl = docWorker ? docWorker.internalUrl : getUrlFromPrefix(server.getHomeInternalUrl(), selfPrefix);
+  const apiBaseUrl = docWorkerUrl.replace(/\/*$/, '/');
+
+  // Documents with external attachments can't be copied right now. Check status and alert the user.
+  // Copying as a template is fine, as no attachments will be copied.
+  if (!template) {
+    const transferStatusResponse = await fetch(
+      new URL(`/api/docs/${docId}/attachments/transferStatus`, apiBaseUrl).href,
+      {
+        headers: {
+          ...headers,
+          'Content-Type': 'application/json',
+        }
+      }
+    );
+    if (!transferStatusResponse.ok) {
+      throw new ApiError(await transferStatusResponse.text(), transferStatusResponse.status);
+    }
+    const attachmentsLocation: DocAttachmentsLocation = (await transferStatusResponse.json()).locationSummary;
+    if (attachmentsLocation !== 'internal' && attachmentsLocation !== 'none') {
+      throw new ApiError("Cannot copy a document with external attachments", 400);
+    }
+  }
+
   // Download the document, in full or as a template.
-  const url = new URL(`api/docs/${docId}/download?template=${Number(template)}`,
-                      docWorkerUrl.replace(/\/*$/, '/'));
+  const url = new URL(`api/docs/${docId}/download?template=${Number(template)}`, apiBaseUrl);
   return _fetchURL(url.href, accessId, {headers});
 }
 
diff --git a/test/server/lib/DocApi.ts b/test/server/lib/DocApi.ts
index e72b1abf13..06622b75d5 100644
--- a/test/server/lib/DocApi.ts
+++ b/test/server/lib/DocApi.ts
@@ -2433,23 +2433,32 @@ function testDocApi(settings: {
 
   });
 
+  async function addAttachmentsToDoc(docId: string, attachments: {name: string, contents: string}[],
+                                     user: AxiosRequestConfig = chimpy) {
+    const formData = new FormData();
+    for (const attachment of attachments) {
+      formData.append('upload', attachment.contents, attachment.name);
+    }
+    const resp = await axios.post(`${serverUrl}/api/docs/${docId}/attachments`, formData,
+      defaultsDeep({headers: formData.getHeaders()}, user));
+    assert.equal(resp.status, 200);
+    assert.equal(resp.data.length, attachments.length);
+    return resp;
+  }
+
   describe('attachments', function () {
     it("POST /docs/{did}/attachments adds attachments", async function () {
-      let formData = new FormData();
-      formData.append('upload', 'foobar', "hello.doc");
-      formData.append('upload', '123456', "world.jpg");
-      let resp = await axios.post(`${serverUrl}/api/docs/${docIds.TestDoc}/attachments`, formData,
-        defaultsDeep({headers: formData.getHeaders()}, chimpy));
-      assert.equal(resp.status, 200);
-      assert.deepEqual(resp.data, [1, 2]);
+      const uploadResp = await addAttachmentsToDoc(docIds.TestDoc, [
+        { name: 'hello.doc', contents: 'foobar' },
+        { name: 'world.jpg', contents: '123456' },
+      ], chimpy);
+      assert.deepEqual(uploadResp.data, [1, 2]);
 
       // Another upload gets the next number.
-      formData = new FormData();
-      formData.append('upload', 'abcdef', "hello.png");
-      resp = await axios.post(`${serverUrl}/api/docs/${docIds.TestDoc}/attachments`, formData,
-        defaultsDeep({headers: formData.getHeaders()}, chimpy));
-      assert.equal(resp.status, 200);
-      assert.deepEqual(resp.data, [3]);
+      const upload2Resp = await addAttachmentsToDoc(docIds.TestDoc, [
+        { name: 'hello.png', contents: 'abcdef' },
+      ], chimpy);
+      assert.deepEqual(upload2Resp.data, [3]);
     });
 
     it("GET /docs/{did}/attachments lists attachment metadata", async function () {
@@ -2753,13 +2762,11 @@ function testDocApi(settings: {
         docId = await userApi.newDoc({name: 'TestDocExternalAttachments'}, wid);
         docUrl = `${serverUrl}/api/docs/${docId}`;
 
-        const formData = new FormData();
-        formData.append('upload', 'foobar', "hello.doc");
-        formData.append('upload', '123456', "world.jpg");
-        formData.append('upload', 'foobar', "hello2.doc");
-        const resp = await axios.post(`${docUrl}/attachments`, formData,
-          defaultsDeep({headers: formData.getHeaders()}, chimpy));
-        assert.equal(resp.status, 200);
+        const resp = await addAttachmentsToDoc(docId, [
+          { name: 'hello.doc', contents: 'foobar' },
+          { name: 'world.jpg', contents: '123456' },
+          { name: 'hello2.doc', contents: 'foobar' }
+        ], chimpy);
         assert.deepEqual(resp.data, [1, 2, 3]);
       });
 
@@ -2804,6 +2811,23 @@ function testDocApi(settings: {
           locationSummary: "internal",
         });
       });
+
+      it("POST /docs/{did}/copy fails when the document has external attachments", async function () {
+        const worker1 = await userApi.getWorkerAPI(docId);
+        await assert.isRejected(worker1.copyDoc(docId, undefined, 'copy'), /status 400/);
+      });
+
+      it("POST /docs/{did} with sourceDocId fails to copy a document with external attachments", async function () {
+        const chimpyWs = await userApi.newWorkspace({name: "Chimpy's Workspace"}, ORG_NAME);
+        const resp = await axios.post(`${serverUrl}/api/docs`, {
+          sourceDocumentId: docId,
+          documentName: 'copy of TestDocExternalAttachments',
+          asTemplate: false,
+          workspaceId: chimpyWs
+        }, chimpy);
+        assert.equal(resp.status, 400);
+        assert.match(resp.data.error, /external attachments/);
+      });
     });
   });