diff --git a/backend/s3/s3.go b/backend/s3/s3.go
index 48f7beaa6..40f157179 100644
--- a/backend/s3/s3.go
+++ b/backend/s3/s3.go
@@ -28,6 +28,11 @@ type S3 struct {
 	path   string
 }
 
+// Open a backend using an S3 bucket object
+func OpenS3Bucket(bucket *s3.Bucket, bucketname string) *S3 {
+	return &S3{bucket: bucket, path: bucketname}
+}
+
 // Open opens the s3 backend at bucket and region.
 func Open(regionname, bucketname string) (*S3, error) {
 	auth, err := aws.EnvAuth()
diff --git a/backend/s3_test.go b/backend/s3_test.go
index 84b4d6d74..68cf8a079 100644
--- a/backend/s3_test.go
+++ b/backend/s3_test.go
@@ -23,7 +23,7 @@ func setupS3Backend(t *testing.T) *bes3.S3 {
 
 	t.Logf("created s3 backend locally at %s", testServer.URL)
 
-	return bes3.S3{bucket: bucket, path: "testbucket"}
+	return bes3.OpenS3Bucket(bucket, "testbucket")
 }
 
 func teardownS3Backend(t *testing.T, b *bes3.S3) {