diff --git a/Dockerfile b/Dockerfile
index aabe386..df2c763 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM lsiobase/nginx:3.11
+FROM lsiobase/nginx:3.12
 
 # set version label
 ARG BUILD_DATE
diff --git a/Dockerfile.aarch64 b/Dockerfile.aarch64
index 3ff0607..21bbf56 100644
--- a/Dockerfile.aarch64
+++ b/Dockerfile.aarch64
@@ -1,4 +1,4 @@
-FROM lsiobase/nginx:arm64v8-3.11
+FROM lsiobase/nginx:arm64v8-3.12
 
 # set version label
 ARG BUILD_DATE
diff --git a/Dockerfile.armhf b/Dockerfile.armhf
index 6ea2e6c..93655a2 100644
--- a/Dockerfile.armhf
+++ b/Dockerfile.armhf
@@ -1,4 +1,4 @@
-FROM lsiobase/nginx:arm32v7-3.11
+FROM lsiobase/nginx:arm32v7-3.12
 
 # set version label
 ARG BUILD_DATE
diff --git a/README.md b/README.md
index ce3daa5..da18bff 100644
--- a/README.md
+++ b/README.md
@@ -265,6 +265,7 @@ Once registered you can define the dockerfile to use with `-f Dockerfile.aarch64
 
 ## Versions
 
+* **17.09.20:** - Rebase to alpine 3.12. Fix APP_URL setting. Bump php post max and upload max filesizes to 100MB by default.
 * **19.12.19:** - Rebasing to alpine 3.11.
 * **26.07.19:** - Use old version of tidyhtml pending upstream fixes.
 * **28.06.19:** - Rebasing to alpine 3.10.
diff --git a/readme-vars.yml b/readme-vars.yml
index 1bac271..362fbf6 100644
--- a/readme-vars.yml
+++ b/readme-vars.yml
@@ -100,6 +100,7 @@ app_setup_block: |
 
 # changelog
 changelogs:
+  - { date: "17.09.20:", desc: "Rebase to alpine 3.12. Fix APP_URL setting. Bump php post max and upload max filesizes to 100MB by default." }
   - { date: "19.12.19:", desc: "Rebasing to alpine 3.11." }
   - { date: "26.07.19:", desc: "Use old version of tidyhtml pending upstream fixes." }
   - { date: "28.06.19:", desc: "Rebasing to alpine 3.10." }
diff --git a/root/etc/cont-init.d/50-config b/root/etc/cont-init.d/50-config
index e663f79..0f3c8cb 100644
--- a/root/etc/cont-init.d/50-config
+++ b/root/etc/cont-init.d/50-config
@@ -58,7 +58,11 @@ if [ "${DB_USER}" ];
 fi
 
 # set appurl if detected
-[[ "${APP_URL}" ]] && sed -i "s,#\sAPP_URL.*,APP_URL=${APP_URL},g" /config/www/.env
+[ -n "${APP_URL}" ] && sed -r "s,([#\s]*)?APP_URL=.*,APP_URL=${APP_URL},g" -i /config/www/.env
+
+## Bump php upload max filesize and post max size to 100MB by default
+grep -qxF 'upload_max_filesize' /config/php/php-local.ini || echo 'upload_max_filesize = 100MB' >> /config/php/php-local.ini
+grep -qxF 'post_max_size' /config/php/php-local.ini || echo 'post_max_size = 100MB' >> /config/php/php-local.ini
 
 # check for the mysql endpoint for 30 seconds
 END=$((SECONDS+30))