diff --git a/nginx/snippets/security-headers.conf b/nginx/snippets/security-headers.conf
index 5901fa2..4110c9f 100644
--- a/nginx/snippets/security-headers.conf
+++ b/nginx/snippets/security-headers.conf
@@ -1,3 +1,5 @@
 add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
 add_header X-Content-Type-Options "nosniff" always;
+
+# obsolete when client system time is correct
 add_header Expect-CT "enforce, max-age=63072000" always;