diff --git a/scripts/paycheck.py b/scripts/paycheck.py
index 5290e9d..0195f53 100755
--- a/scripts/paycheck.py
+++ b/scripts/paycheck.py
@@ -117,7 +117,7 @@
         parser.error('invalid argument to --disabled_tests: %s' % test)
 
   # Ensure consistent use of block tracing options.
-  do_block_trace = opts.root_block or opts.kern_block
+  do_block_trace = not (opts.root_block is None and opts.kern_block is None)
   if opts.skip and not do_block_trace:
     parser.error('--skip must be used with either --root-block or --kern-block')