diff --git a/llvm/utils/update_test_checks.py b/llvm/utils/update_test_checks.py
--- a/llvm/utils/update_test_checks.py
+++ b/llvm/utils/update_test_checks.py
@@ -71,7 +71,6 @@
     if not re.match(r'^%s(-\d+)?(\.exe)?$' % (initial_args.tool), tool_basename):
       common.error('Unexpected tool name: ' + tool_basename)
       sys.exit(1)
-  tool_basename = initial_args.tool
 
   for ti in common.itertests(initial_args.tests, parser,
                              script_name='utils/' + script_name):
@@ -81,6 +80,8 @@
     else:
       common.SCRUB_TRAILING_WHITESPACE_TEST_RE = common.SCRUB_TRAILING_WHITESPACE_RE
 
+    tool_basename = ti.args.tool
+
     prefix_list = []
     for l in ti.run_lines:
       if '|' not in l: