diff --git a/prometheus-alertmanager/Dockerfile b/prometheus-alertmanager/Dockerfile
index c7f1139..f3278ee 100644
--- a/prometheus-alertmanager/Dockerfile
+++ b/prometheus-alertmanager/Dockerfile
@@ -1,3 +1,3 @@
-FROM prom/alertmanager:v0.21.0
+FROM prom/alertmanager:v0.20.0
 
 COPY alertmanager.yml /etc/alertmanager/alertmanager.yml