diff --git a/apps/viewer/src/legacy.spec.ts b/apps/viewer/src/legacy.spec.ts
index 40679ec5ea286..f4e8827d64fdd 100644
--- a/apps/viewer/src/legacy.spec.ts
+++ b/apps/viewer/src/legacy.spec.ts
@@ -110,6 +110,27 @@ describe('OCA.Viewer compatibility layer', () => {
 		expect(target.basename).toBe('pineapple.jpg')
 	})
 
+	it('addresses a file with a dav source relative to its dav home', async () => {
+		await viewer().open({
+			fileInfo: { source: 'https://cloud.example/remote.php/dav/files/emma/Photos/2019/x.jpg', filename: '/Photos/2019/x.jpg', mime: 'image/jpeg' },
+		})
+
+		const [, target] = viewerOpen.mock.calls[0]
+		expect(target.source).toBe('https://cloud.example/remote.php/dav/files/emma/Photos/2019/x.jpg')
+		expect(target.root).toBe('/files/emma')
+		expect(target.path).toBe('/Photos/2019/x.jpg')
+	})
+
+	it('addresses a file of another dav service relative to its home there', async () => {
+		await viewer().open({
+			fileInfo: { source: 'https://cloud.example/remote.php/dav/photos/emma/albums/Trip/x.jpg', mime: 'image/jpeg' },
+		})
+
+		const [, target] = viewerOpen.mock.calls[0]
+		expect(target.root).toBe('/photos/emma')
+		expect(target.basename).toBe('x.jpg')
+	})
+
 	it('passes the handler on to openWith', async () => {
 		await viewer().openWith('richdocuments', { fileInfo: { fileid: 1, filename: '/a.pdf', mime: 'application/pdf' } })
 		expect(viewerOpen.mock.calls[0][3]).toBe('richdocuments')
diff --git a/apps/viewer/src/legacy.ts b/apps/viewer/src/legacy.ts
index 0681dafb69885..e884f45c8cd07 100644
--- a/apps/viewer/src/legacy.ts
+++ b/apps/viewer/src/legacy.ts
@@ -145,12 +145,33 @@ function directoryOf(source: string): string {
 	}
 }
 
+/**
+ * The root a node served from an address is relative to.
+ *
+ * An address on dav sits under a home of one of its services, such as
+ * `/files/emma`, and a node has to be relative to that home. Anything else
+ * has no home, so the folder the file sits in stands in for it and the node
+ * still knows its own name.
+ *
+ * @param source - the address the file is served from
+ */
+function rootOf(source: string): string {
+	const davRemote = getRemoteURL() + '/'
+	if (source.startsWith(davRemote)) {
+		const [service, home] = source.slice(davRemote.length).split('/')
+		if (service && home) {
+			return `/${service}/${home}`
+		}
+	}
+	return directoryOf(source)
+}
+
 /**
  * Build a node out of what an app handed over.
  *
  * Callers filled in what they had, so most of this is defaulting. A file
- * with a `source` of its own is served from somewhere that is not dav, and
- * keeps it; everything else is addressed under the user's files.
+ * with a `source` of its own keeps it; everything else is addressed under
+ * the user's files.
  *
  * @param info - the file info an app passed to open
  */
@@ -169,10 +190,7 @@ function nodeFromFileInfo(info: LegacyFileInfo): IFile {
 
 	const data: NodeData = {
 		source,
-		// A file under the user's files is relative to their dav home. One
-		// served from somewhere else has no home, so the folder it sits in
-		// stands in for it and the node still knows its own name.
-		root: info.source === undefined ? getRootPath() : directoryOf(info.source),
+		root: info.source === undefined ? getRootPath() : rootOf(info.source),
 		displayname: info.basename ?? basenameOf(source),
 		mime: info.mime ?? 'application/octet-stream',
 		owner,