diff --git a/compose.mailman.yml b/compose.mailman.yml
index 79188f6..a600f9c 100644
--- a/compose.mailman.yml
+++ b/compose.mailman.yml
@@ -1,4 +1,4 @@
-version: "3.6"
+version: "3.8"
 
 # TODO(decentral1se): rename `postfix_override` to `mailman_override` because
 #                     there are more override files now and it is good to be
diff --git a/compose.senderlogins.yml b/compose.senderlogins.yml
index 2895257..aa4d5c4 100644
--- a/compose.senderlogins.yml
+++ b/compose.senderlogins.yml
@@ -1,4 +1,4 @@
-version: "3.6"
+version: "3.8"
 
 services:
   smtp:
diff --git a/compose.yml b/compose.yml
index b8dcf14..c53264e 100644
--- a/compose.yml
+++ b/compose.yml
@@ -1,4 +1,4 @@
-version: '3.6'
+version: "3.8"
 
 x-environment:
   &default-env