fixed printing queue messages
diff --git a/aos/build/queues/print_field.rb b/aos/build/queues/print_field.rb
index c7b8530..75cc1da 100644
--- a/aos/build/queues/print_field.rb
+++ b/aos/build/queues/print_field.rb
@@ -75,7 +75,7 @@
         if (*output_bytes < 1) return false;
         *input_bytes -= 1;
         bool value = static_cast<const char *>(input)[0];
-        *output_bytes += 1;
+        *output_bytes -= 1;
         *output = value ? 'T' : 'f';
         return true;
       }