diff --git a/README.md b/README.md
index 7bd263b..fe186dc 100644
--- a/README.md
+++ b/README.md
@@ -28,8 +28,9 @@
 
 ## ToDo:
 - [x] Add CI tests to make sure the scripts work.
+- [x] Make PBKEY a required variable to avoid running uam without it.
 - [ ] Remove unnecessary packages.
 - [ ] Try to speed up mime database update.
-- [ ] Include wondershaper in `apt install` and environment configuration parameters for it.
+- [ ] Include wondershaper or sch_cake in `apt install` and environment configuration parameters for it.
 - [ ] See if it's possible to automatically increment port numbers for the swarm script.
 - [ ] Try to package up-to-date databases to prevent warm-up problems.
diff --git a/uam-swarm/docker-compose.yml b/uam-swarm/docker-compose.yml
index 42acaa2..fbcb158 100644
--- a/uam-swarm/docker-compose.yml
+++ b/uam-swarm/docker-compose.yml
@@ -20,7 +20,7 @@ services:
       - "127.0.0.1:17100:17099"
       - "4160:4160"
     environment:
-      - PBKEY=$PBKEY
+      - PBKEY=${PBKEY?err}
       - PPORT=4160
 
   uam_2:
@@ -42,7 +42,7 @@ services:
       - "127.0.0.1:17101:17099"
       - "4161:4161"
     environment:
-      - PBKEY=$PBKEY
+      - PBKEY=${PBKEY?err}
       - PPORT=4161
 
   uam_3:
@@ -64,5 +64,5 @@ services:
       - "127.0.0.1:17102:17099"
       - "4162:4162"
     environment:
-      - PBKEY=$PBKEY
+      - PBKEY=${PBKEY?err}
       - PPORT=4162
diff --git a/uam/docker-compose.yml b/uam/docker-compose.yml
index 2d05fcb..4c1f115 100644
--- a/uam/docker-compose.yml
+++ b/uam/docker-compose.yml
@@ -20,4 +20,4 @@ services:
       - "127.0.0.1:17099:17099"
       - "4156:4156"
     environment:
-      - PBKEY=$PBKEY
+      - PBKEY=${PBKEY?err}