diff --git a/core/postfix/Dockerfile b/core/postfix/Dockerfile
index bb5831a2..168f3c60 100644
--- a/core/postfix/Dockerfile
+++ b/core/postfix/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.7
 
 RUN apk add --no-cache postfix postfix-sqlite postfix-pcre rsyslog python py-jinja2