diff --git a/main/nginx/APKBUILD b/main/nginx/APKBUILD
index c29428ec7b6..ec661b5b684 100644
--- a/main/nginx/APKBUILD
+++ b/main/nginx/APKBUILD
@@ -8,6 +8,8 @@
 #     - CVE-2017-7529
 #
 pkgname=nginx
+# NOTE: Upgrade only to even-numbered versions (e.g. 1.14.z, 1.16.z)!
+# Odd-numbered versions are mainline (development) versions.
 pkgver=1.14.0
 pkgrel=0
 # Revision of nginx-tests to use for check().