diff --git a/monitoring.yml b/monitoring.yml
index 13fcbb99..4a740896 100644
--- a/monitoring.yml
+++ b/monitoring.yml
@@ -88,7 +88,7 @@ services:
       - monitoring
 
   cadvisor:
-    image: $(CADVISOR_IMAGE:-gcr.io/cadvisor/cadvisor:v0.49.1}
+    image: ${CADVISOR_IMAGE:-gcr.io/cadvisor/cadvisor:v0.49.1}
     container_name: cadvisor
     privileged: true
     devices: