diff --git a/backup.nix b/backup.nix
index bbc5e0c..f06660e 100644
--- a/backup.nix
+++ b/backup.nix
@@ -31,7 +31,7 @@ let
       bucket="$(grep 'bucket=' < "$configFile" | sed 's/bucket \?= \?')"
       prefix="$(grep 'prefix=' < "$configFile" | sed 's/prefix \?= \?')"
 
-      s3Dir="s3://$bucket/\${prefix}misskey-$(date --iso-8601)"
+      s3Dir="s3://$bucket/$prefix""misskey-$(date --iso-8601)"
       echo "Uploading backups to '$s3Dir'"
 
       function upload () {