diff --git a/doc/manual.rst b/doc/manual.rst
index 3e205e6c1..6841deb21 100644
--- a/doc/manual.rst
+++ b/doc/manual.rst
@@ -405,11 +405,22 @@ established.
 Google Cloud Storage
 ~~~~~~~~~~~~~~~~~~~~
 
-Restic supports Google Cloud Storage as a backend. In order for this to work
-you first need create a "service account" and download the JSON key file for
-it. In addition, you need the Google Project ID that you can see in the Google
+Restic supports Google Cloud Storage as a backend.
+
+Restic connects to Google Cloud Storage via a `service account`_.
+
+For normal restic operation, the service account must have the
+``storage.objects.{create,delete,get,list}`` permissions for the bucket. These
+are included in the "Storage Object Admin" role. For ``restic init``, the
+service account must also have the ``storage.buckets.get`` and
+``storage.buckets.create`` (if the bucket does not exist) permissions. These
+are included in the "Storage Admin" role.
+
+`Create a service account key`_ and download the JSON credentials file.
+
+In addition, you need the Google Project ID that you can see in the Google
 Cloud Platform console at the "Storage/Settings" menu. Export the path to the
-JSON credentials file and the project ID as follows:
+JSON key file and the project ID as follows:
 
 .. code-block:: console
 
@@ -432,6 +443,9 @@ The number of concurrent connections to the GCS service can be set with the
 `-o gs.connections=10`. By default, at most five parallel connections are
 established.
 
+.. _service account: https://cloud.google.com/storage/docs/authentication#service_accounts
+.. _Create a service account key: https://cloud.google.com/storage/docs/authentication#generating-a-private-key
+
 
 Password prompt on Windows
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/internal/backend/gs/config.go b/internal/backend/gs/config.go
index cc1b7d805..eebd4fe23 100644
--- a/internal/backend/gs/config.go
+++ b/internal/backend/gs/config.go
@@ -8,8 +8,8 @@ import (
 	"github.com/restic/restic/internal/options"
 )
 
-// Config contains all configuration necessary to connect to an gcs compatible
-// server.
+// Config contains all configuration necessary to connect to a Google Cloud
+// Storage bucket.
 type Config struct {
 	ProjectID   string
 	JSONKeyPath string
diff --git a/internal/backend/gs/gs.go b/internal/backend/gs/gs.go
index 902726d1b..ea003d955 100644
--- a/internal/backend/gs/gs.go
+++ b/internal/backend/gs/gs.go
@@ -1,3 +1,4 @@
+// Package gs provides a restic backend for Google Cloud Storage.
 package gs
 
 import (
@@ -20,7 +21,13 @@ import (
 	storage "google.golang.org/api/storage/v1"
 )
 
-// Backend stores data on an gs endpoint.
+// Backend stores data in a GCS bucket.
+//
+// The service account used to access the bucket must have these permissions:
+//  * storage.objects.create
+//  * storage.objects.delete
+//  * storage.objects.get
+//  * storage.objects.list
 type Backend struct {
 	service      *storage.Service
 	projectID    string
@@ -31,7 +38,7 @@ type Backend struct {
 	backend.Layout
 }
 
-// make sure that *Backend implements backend.Backend
+// Ensure that *Backend implements restic.Backend.
 var _ restic.Backend = &Backend{}
 
 func getStorageService(jsonKeyPath string) (*storage.Service, error) {
@@ -87,21 +94,25 @@ func open(cfg Config) (*Backend, error) {
 	return be, nil
 }
 
-// Open opens the gs backend at bucket and region.
+// Open opens the gs backend at the specified bucket.
 func Open(cfg Config) (restic.Backend, error) {
 	return open(cfg)
 }
 
-// Create opens the S3 backend at bucket and region and creates the bucket if
-// it does not exist yet.
+// Create opens the gs backend at the specified bucket and creates the bucket
+// if it does not exist yet.
+//
+// In addition to the permissions required by Backend, Create requires these
+// permissions:
+//  * storage.buckets.get
+//  * storage.buckets.create (if the bucket doesn't exist)
 func Create(cfg Config) (restic.Backend, error) {
 	be, err := open(cfg)
-
 	if err != nil {
 		return nil, errors.Wrap(err, "open")
 	}
 
-	// Create bucket if not exists
+	// Create bucket if it doesn't exist.
 	if _, err := be.service.Buckets.Get(be.bucketName).Do(); err != nil {
 		bucket := &storage.Bucket{
 			Name: be.bucketName,
@@ -371,5 +382,5 @@ func (be *Backend) Delete(ctx context.Context) error {
 	return be.Remove(ctx, restic.Handle{Type: restic.ConfigFile})
 }
 
-// Close does nothing
+// Close does nothing.
 func (be *Backend) Close() error { return nil }