diff --git a/Dockerfile-debian.template b/Dockerfile-debian.template
index 5d0a4812..7257d876 100644
--- a/Dockerfile-debian.template
+++ b/Dockerfile-debian.template
@@ -1,4 +1,4 @@
-FROM php:%%PHP_VERSION%%-%%VARIANT%%-buster
+FROM php:%%PHP_VERSION%%-%%VARIANT%%-bullseye
 
 # entrypoint.sh and cron.sh dependencies
 RUN set -ex; \