Can't use variable in ExecStart command
diff --git a/aptly/files/aptly-api.service b/aptly/files/aptly-api.service
index 011dd19..9e44fda 100644
--- a/aptly/files/aptly-api.service
+++ b/aptly/files/aptly-api.service
@@ -1,3 +1,9 @@
+{%- from "aptly/map.jinja" import server with context -%}
+{%- if server.source.engine == 'docker' -%}
+    {%- set command="/usr/local/bin/aptly" -%}
+{%- else -%}
+    {%- set command="/usr/bin/aptly" -%}
+{%- endif -%}
 [Unit]
 Description=Aptly API server
 Requires=network-online.target
@@ -6,7 +12,7 @@
 [Service]
 User=aptly
 EnvironmentFile=/etc/default/aptly-api
-ExecStart=${COMMAND} api serve -listen=${LISTEN_HOST}:${LISTEN_PORT}
+ExecStart={{ command }} api serve -listen=${LISTEN_HOST}:${LISTEN_PORT}
 Restart=on-failure
 
 [Install]
diff --git a/aptly/server/api.sls b/aptly/server/api.sls
index 70e0dcc..efb4bbd 100644
--- a/aptly/server/api.sls
+++ b/aptly/server/api.sls
@@ -9,6 +9,7 @@
   file.managed:
     - name: /etc/systemd/system/aptly-api.service
     - source: salt://aptly/files/aptly-api.service
+    - template: jinja
     - user: root
     - group: root
     - require: