diff --git a/.env.example b/.env.example
index f4d6e70857..1ce3227e23 100644
--- a/.env.example
+++ b/.env.example
@@ -179,6 +179,9 @@ AUTHENTICATION_GUARD=web
 # Some systems use X-Auth headers. In that case, use HTTP_X_AUTH_USERNAME or HTTP_X_AUTH_EMAIL
 # Depending on your system, REMOTE_USER may need to be changed to HTTP_REMOTE_USER
 #
+# If this header is 'unexpectedly empty', check out the documentation.
+# https://docs.firefly-iii.org/advanced-installation/authentication
+#
 AUTHENTICATION_GUARD_HEADER=REMOTE_USER
 
 #