diff --git a/outline/docker-compose.yaml b/outline/docker-compose.yaml
index 1f71dcf..04f920a 100644
--- a/outline/docker-compose.yaml
+++ b/outline/docker-compose.yaml
@@ -1,3 +1,4 @@
+version: "3.8"
 services:
   outline_redis:
     image: redis@sha256:7614ae9453d1d87e740a2056257a6de7135c84037c367e1fffa92ae922784631