diff --git a/roles/container/defaults/main.yml b/roles/container/defaults/main.yml
index cf6a33d..8f70550 100644
--- a/roles/container/defaults/main.yml
+++ b/roles/container/defaults/main.yml
@@ -3,6 +3,7 @@
 docker_host_user: false
 docker_volume_type: named
 docker_mariadb_config: {}
+dockerfile: []
 
 docker_phpmyadmin_basicauth: true
 docker_phpmyadmin_basicauth_users: {}
diff --git a/roles/container/meta/argument_specs.yml b/roles/container/meta/argument_specs.yml
index a4d2112..0c7f00f 100644
--- a/roles/container/meta/argument_specs.yml
+++ b/roles/container/meta/argument_specs.yml
@@ -17,6 +17,12 @@ argument_specs:
         description: "Docker image to use for the container. If dockerfile is defined, it will be used as base for locally built image (example: gitea/gitea:latest)"
         type: str
         required: true
+      dockerfile:
+        description: "A list of dockerfile instructions to add to the base image"
+        type: list
+        elements: str
+        required: false
+        default: []
       docker_host_user:
         description: "If true, creates a user on the host for this service. The container will run as this user's uid/gid. Bind mount volumes will be owned by this user."
         type: bool
diff --git a/roles/container/tasks/init.yml b/roles/container/tasks/init.yml
index 2b3c327..c131a53 100644
--- a/roles/container/tasks/init.yml
+++ b/roles/container/tasks/init.yml
@@ -39,7 +39,7 @@
   set_fact:
     template_mounts_needed: "{{ docker_mounts | selectattr('template', 'defined') | list | length > 0 }}"
     volumes_needed: "{{ docker_mounts | selectattr('name', 'defined') | list | length > 0 or docker_database != 'none' }}"
-    dockerfile_needed: "{{ dockerfile is defined and dockerfile | length > 0 }}"
+    dockerfile_needed: "{{ dockerfile | length > 0 }}"
     db_config_mounts_needed: "{{ docker_mariadb_config | length > 0 }}"
 - name: Set more assistive variables
   set_fact:
diff --git a/roles/container/templates/Dockerfile.j2 b/roles/container/templates/Dockerfile.j2
index 74befcd..ed52e63 100644
--- a/roles/container/templates/Dockerfile.j2
+++ b/roles/container/templates/Dockerfile.j2
@@ -1,9 +1,6 @@
 # {{ ansible_managed }}
 
 FROM {{ docker_image }}
-{% if dockerfile.run is iterable %}
-{% for cmd in dockerfile.run %}
-RUN {{ cmd }}
+{% for item in dockerfile %}
+{{ item }}
 {% endfor %}
-{% endif %}
-
diff --git a/roles/wordpress/tasks/main.yml b/roles/wordpress/tasks/main.yml
index fed51b8..0a77772 100644
--- a/roles/wordpress/tasks/main.yml
+++ b/roles/wordpress/tasks/main.yml
@@ -2,7 +2,7 @@
 
 - name: Reset dockerfile variable
   set_fact:
-    dockerfile: {}
+    dockerfile: []
 
 - name: Set docker service full name (required because docker_env uses it)
   set_fact:
@@ -11,14 +11,16 @@
 
 - name: Add memcached php extension to container
   set_fact:
-    dockerfile: "{{ dockerfile | combine({'run': \
-      ['apt-get update && apt-get install -y libmemcached-dev libssl-dev zlib1g-dev && \
-      pecl install memcached-3.2.0 && docker-php-ext-enable memcached']}, list_merge='append') }}"
+    dockerfile: >
+      "{{ dockerfile +
+      ['RUN apt-get update && \
+      apt-get install -y libmemcached-dev libssl-dev zlib1g-dev && \
+      pecl install memcached-3.2.0 && docker-php-ext-enable memcached'] }}"
   when: "'memcached' in docker_additional_services"
 
 - name: Add pdo_mysql php extension to container
   set_fact:
-    dockerfile: "{{ dockerfile | combine({'run': ['docker-php-ext-install -j$(nproc) pdo_mysql']}, list_merge='append') }}"
+    dockerfile: "{{ dockerfile + ['RUN docker-php-ext-install -j$(nproc) pdo_mysql'] }}"
   when: "'pdo_mysql' in wordpress_php_extensions"
 
 - name: Include additional volume vars