diff --git a/backup.nix b/backup.nix
index 6f208da..d71b37e 100644
--- a/backup.nix
+++ b/backup.nix
@@ -28,10 +28,10 @@ let
       s3cfg="$2"
 
       ageRecipient="age17ckyc69njpryytc63ynn545jswyucg28k5xg3043g3j6q38dxqwq0wzhm2"
-      bucket="$(cat "$configFile" | grep 'bucket=' | sed 's/bucket \?= \?')"
-      prefix="$(cat "$configFile" | grep 'prefix=' | sed 's/prefix \?= \?')"
+      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 () {