diff --git a/x-govuk/components/primary-navigation/_primary-navigation.scss b/x-govuk/components/primary-navigation/_primary-navigation.scss
index 5fa7307..0648f81 100644
--- a/x-govuk/components/primary-navigation/_primary-navigation.scss
+++ b/x-govuk/components/primary-navigation/_primary-navigation.scss
@@ -1,3 +1,5 @@
+@warn "Primary navigation component styles are deprecated, and will be removed in v4.0. Use the service navigation component from the GOV.UK Design System instead.";
+
 .x-govuk-primary-navigation {
   @include govuk-font(19, $weight: bold);
   background-color: govuk-colour("light-grey");