diff --git a/crypto/hmac_extra/hmac_tests.txt b/crypto/hmac_extra/hmac_tests.txt
index 1d7efd2ad..1339b5b39 100644
--- a/crypto/hmac_extra/hmac_tests.txt
+++ b/crypto/hmac_extra/hmac_tests.txt
@@ -33,6 +33,7 @@ Input = "Sample message for keylen<blocklen"
 Key = 000102030405060708090A0B0C0D0E0F10111213
 Output = 4C99FF0CB1B31BD33F8431DBAF4D17FCD356A807
 
+# This is actually keylen>blocklen, but the NIST test vectors have a misleading input.
 HMAC = SHA1
 Input = "Sample message for keylen=blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F60616263
@@ -48,6 +49,7 @@ Input = "Sample message for keylen<blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B
 Output = E3D249A8CFB67EF8B7A169E9A0A599714A2CECBA65999A51BEB8FBBE
 
+# This is actually keylen>blocklen, but the NIST test vectors have a misleading input.
 HMAC = SHA224
 Input = "Sample message for keylen=blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F60616263
@@ -63,6 +65,7 @@ Input = "Sample message for keylen<blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F
 Output = A28CF43130EE696A98F14A37678B56BCFCBDD9E5CF69717FECF5480F0EBDF790
 
+# This is actually keylen>blocklen, but the NIST test vectors have a misleading input.
 HMAC = SHA256
 Input = "Sample message for keylen=blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F60616263
@@ -78,6 +81,7 @@ Input = "Sample message for keylen<blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F
 Output = 6EB242BDBB582CA17BEBFA481B1E23211464D2B7F8C20B9FF2201637B93646AF5AE9AC316E98DB45D9CAE773675EEED0
 
+# This is actually keylen>blocklen, but the NIST test vectors have a misleading input.
 HMAC = SHA384
 Input = "Sample message for keylen=blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F606162636465666768696A6B6C6D6E6F707172737475767778797A7B7C7D7E7F808182838485868788898A8B8C8D8E8F909192939495969798999A9B9C9D9E9FA0A1A2A3A4A5A6A7A8A9AAABACADAEAFB0B1B2B3B4B5B6B7B8B9BABBBCBDBEBFC0C1C2C3C4C5C6C7
@@ -93,6 +97,7 @@ Input = "Sample message for keylen<blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F
 Output = FD44C18BDA0BB0A6CE0E82B031BF2818F6539BD56EC00BDC10A8A2D730B3634DE2545D639B0F2CF710D0692C72A1896F1F211C2B922D1A96C392E07E7EA9FEDC
 
+# This is actually keylen>blocklen, but the NIST test vectors have a misleading input.
 HMAC = SHA512
 Input = "Sample message for keylen=blocklen"
 Key = 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F606162636465666768696A6B6C6D6E6F707172737475767778797A7B7C7D7E7F808182838485868788898A8B8C8D8E8F909192939495969798999A9B9C9D9E9FA0A1A2A3A4A5A6A7A8A9AAABACADAEAFB0B1B2B3B4B5B6B7B8B9BABBBCBDBEBFC0C1C2C3C4C5C6C7