diff --git a/backend/s3/s3.go b/backend/s3/s3.go
index 473f74ece..9183670c4 100644
--- a/backend/s3/s3.go
+++ b/backend/s3/s3.go
@@ -3222,6 +3222,10 @@ func setQuirks(opt *Options) {
 		// https://github.com/rclone/rclone/issues/6670
 		useAcceptEncodingGzip = false
 		useAlreadyExists = true // returns BucketNameUnavailable instead of BucketAlreadyExists but good enough!
+		// GCS S3 doesn't support multi-part server side copy:
+		// See: https://issuetracker.google.com/issues/323465186
+		// So make cutoff very large which it does seem to support
+		opt.CopyCutoff = math.MaxInt64
 	default:
 		fs.Logf("s3", "s3 provider %q not known - please set correctly", opt.Provider)
 		fallthrough