diff --git a/home/scripts/reporsync.nix b/home/scripts/reporsync.nix
index e52479a..0bbef43 100644
--- a/home/scripts/reporsync.nix
+++ b/home/scripts/reporsync.nix
@@ -36,7 +36,7 @@ _parse_rsync_args() {
 	done
 
 	# trim CLI parameters
-	shift "(($OPTIND -1))"
+	shift "$(($OPTIND -1))"
 
 	RR_FROM="$1"
 	RR_TO="$2"