diff --git a/tools/testtool/testdata/submissions/correct/sum/private/sum/sum_private_test.go b/tools/testtool/testdata/submissions/correct/sum/private/sum/sum_private_test.go
index 526f814..394d3ca 100644
--- a/tools/testtool/testdata/submissions/correct/sum/private/sum/sum_private_test.go
+++ b/tools/testtool/testdata/submissions/correct/sum/private/sum/sum_private_test.go
@@ -1,4 +1,4 @@
-// + build private
+// +build private
 
 package sum