diff --git a/tools/buildgen/generate_projects.py b/tools/buildgen/generate_projects.py
index c3e2b120516..e0bd6759bd0 100755
--- a/tools/buildgen/generate_projects.py
+++ b/tools/buildgen/generate_projects.py
@@ -78,8 +78,8 @@ jobset.run(jobs)
 if test is not None:
   for s, g in test.iteritems():
     if os.path.isfile(g):
-      assert(0 == os.system('diff %s %s' % (s, g)))
+      assert 0 == os.system('diff %s %s' % (s, g)), s
       os.unlink(g)
     else:
-      assert(0 == os.system('diff -r %s %s' % (s, g)))
+      assert 0 == os.system('diff -r %s %s' % (s, g)), s
       shutil.rmtree(g, ignore_errors=True)