diff --git a/maintainers/scripts/copy-tarballs.pl b/maintainers/scripts/copy-tarballs.pl
index c81b49bfb599..2f8d250fd529 100755
--- a/maintainers/scripts/copy-tarballs.pl
+++ b/maintainers/scripts/copy-tarballs.pl
@@ -50,19 +50,22 @@ while (@ARGV) {
     }
 }
 
+my $bucket;
 
-# S3 setup.
-my $aws_access_key_id = $ENV{'AWS_ACCESS_KEY_ID'} or die "AWS_ACCESS_KEY_ID not set\n";
-my $aws_secret_access_key = $ENV{'AWS_SECRET_ACCESS_KEY'} or die "AWS_SECRET_ACCESS_KEY not set\n";
+if (not defined $ENV{DEBUG}) {
+    # S3 setup.
+    my $aws_access_key_id = $ENV{'AWS_ACCESS_KEY_ID'} or die "AWS_ACCESS_KEY_ID not set\n";
+    my $aws_secret_access_key = $ENV{'AWS_SECRET_ACCESS_KEY'} or die "AWS_SECRET_ACCESS_KEY not set\n";
 
-my $s3 = Net::Amazon::S3->new(
-    { aws_access_key_id     => $aws_access_key_id,
-      aws_secret_access_key => $aws_secret_access_key,
-      retry                 => 1,
-      host                  => "s3-eu-west-1.amazonaws.com",
-    });
+    my $s3 = Net::Amazon::S3->new(
+        { aws_access_key_id     => $aws_access_key_id,
+          aws_secret_access_key => $aws_secret_access_key,
+          retry                 => 1,
+          host                  => "s3-eu-west-1.amazonaws.com",
+        });
 
-my $bucket = $s3->bucket("nixpkgs-tarballs") or die;
+    $bucket = $s3->bucket("nixpkgs-tarballs") or die;
+}
 
 my $doWrite = 0;
 my $cacheFile = ($ENV{"HOME"} or die "\$HOME is not set") . "/.cache/nix/copy-tarballs";