diff --git a/lib/Qpsmtpd/Transaction.pm b/lib/Qpsmtpd/Transaction.pm
index 602aa93..91553bb 100644
--- a/lib/Qpsmtpd/Transaction.pm
+++ b/lib/Qpsmtpd/Transaction.pm
@@ -84,7 +84,7 @@ sub body_write {
        die "Permissions on the spool_dir are not 0700" if $mode & 07077;
      }
 
-     -d $spool_dir or mkdir($spool_dir, 0700) or die "Could not create spool_dir: $!";
+     -d $spool_dir or mkdir($spool_dir, 0700) or die "Could not create spool_dir $spool_dir: $!";
      $self->{_filename} = $spool_dir . join(":", time, $$, $transaction_counter++);
      $self->{_filename} =~ tr!A-Za-z0-9:/_-!!cd;
     $self->{_body_file} = IO::File->new($self->{_filename}, O_RDWR|O_CREAT, 0600)