diff --git a/apps/dav/lib/CardDAV/SyncService.php b/apps/dav/lib/CardDAV/SyncService.php
index a694172bc49a8..05a08d08286ba 100644
--- a/apps/dav/lib/CardDAV/SyncService.php
+++ b/apps/dav/lib/CardDAV/SyncService.php
@@ -112,6 +112,8 @@ private function prepareUri(string $host, string $path): string {
 		/*
 		 * The trailing slash is important for merging the uris together.
 		 *
+		 * $host is stored in oc_trusted_servers.url and usually without a trailing slash.
+		 *
 		 * Example for a report request
 		 *
 		 * $host = 'https://server.internal/cloud'
@@ -119,6 +121,14 @@ private function prepareUri(string $host, string $path): string {
 		 *
 		 * Without the trailing slash, the webroot is missing:
 		 * https://server.internal/remote.php/dav/addressbooks/system/system/system
+		 *
+		 * Example for a download request
+		 *
+		 * $host = 'https://server.internal/cloud'
+		 * $path = '/cloud/remote.php/dav/addressbooks/system/system/system/Database:alice.vcf'
+		 *
+		 * The response from the remote usually contains the webroot already and must be normalized to:
+		 * https://server.internal/cloud/remote.php/dav/addressbooks/system/system/system/Database:alice.vcf
 		 */
 		$host = rtrim($host, '/') . '/';