diff --git a/test_check.c b/test_check.c
index 906542a9f..713c9b4ea 100644
--- a/test_check.c
+++ b/test_check.c
@@ -2139,6 +2139,7 @@ START_TEST(test_keccak_256)
 }
 END_TEST
 
+// test vectors from https://raw.githubusercontent.com/monero-project/monero/master/tests/hash/tests-extra-blake.txt
 START_TEST(test_blake256)
 {
 	struct {