diff --git a/internal/hmac/vendor.sh b/internal/hmac/vendor.sh
index 83a2b32..c3bffc0 100755
--- a/internal/hmac/vendor.sh
+++ b/internal/hmac/vendor.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+
+# Copy hmac.ho and hmac_test.go from current go distribution.
 cp -v $GOROOT/src/crypto/hmac/{hmac,hmac_test}.go .
 git diff {hmac,hmac_test}.go
-