diff --git a/.env b/.env
index be92335..8d3b28e 100644
--- a/.env
+++ b/.env
@@ -45,3 +45,6 @@ DOMAIN=islandora.dev
 
 # The email to use for admin users and Lets Encrypt.
 EMAIL=postmaster@example.com
+
+# Whether using fcrepo version 6
+FEDORA_6=true
diff --git a/docker-compose.yml b/docker-compose.yml
index 786af67..31d12c9 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -201,6 +201,8 @@ services:
             default:
                 aliases: # Allow access without using the `-dev` or `-prod` suffix.
                     - milliner
+        environment:
+            MILLINER_FEDORA6: ${FEDORA_6}
     milliner-prod:
         <<: [*prod, *milliner]
         secrets: *secrets-jwt-public