diff --git a/core/admin/Dockerfile b/core/admin/Dockerfile
index f0209d3..bdc2bbe 100644
--- a/core/admin/Dockerfile
+++ b/core/admin/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3-alpine
+FROM python:3-alpine3.7
 
 RUN mkdir -p /app
 WORKDIR /app
diff --git a/core/dovecot/Dockerfile b/core/dovecot/Dockerfile
index 9e87f12..0bd6ecf 100644
--- a/core/dovecot/Dockerfile
+++ b/core/dovecot/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:edge
+FROM alpine:3.7
 
 RUN echo "@testing http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories \
  && apk add --no-cache \
diff --git a/core/nginx/Dockerfile b/core/nginx/Dockerfile
index ad6752a..839a1cc 100644
--- a/core/nginx/Dockerfile
+++ b/core/nginx/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:edge
+FROM alpine:3.7
 
 RUN apk add --no-cache nginx nginx-mod-mail python py-jinja2 certbot openssl
 
diff --git a/core/none/Dockerfile b/core/none/Dockerfile
index 979699d..480a615 100644
--- a/core/none/Dockerfile
+++ b/core/none/Dockerfile
@@ -1,5 +1,5 @@
 # This is an idle image to dynamically replace any component if disabled.
 
-FROM alpine
+FROM alpine:3.7
 
 CMD sleep 1000000d
diff --git a/optional/clamav/Dockerfile b/optional/clamav/Dockerfile
index 5b7b99d..eb41f84 100644
--- a/optional/clamav/Dockerfile
+++ b/optional/clamav/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:edge
+FROM alpine:3.7
 
 RUN apk add --no-cache clamav rsyslog wget clamav-libunrar
 
diff --git a/optional/radicale/Dockerfile b/optional/radicale/Dockerfile
index dce888b..6749606 100644
--- a/optional/radicale/Dockerfile
+++ b/optional/radicale/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:edge
+FROM alpine:3.7
 
 RUN echo "@testing http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories \
  && apk add --no-cache radicale@testing py-dulwich@testing
diff --git a/services/fetchmail/Dockerfile b/services/fetchmail/Dockerfile
index a44c6e5..06444ee 100644
--- a/services/fetchmail/Dockerfile
+++ b/services/fetchmail/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:alpine
+FROM python:alpine3.7
 
 RUN apk add --no-cache fetchmail ca-certificates
 
diff --git a/services/rspamd/Dockerfile b/services/rspamd/Dockerfile
index b63d06c..b36be8c 100644
--- a/services/rspamd/Dockerfile
+++ b/services/rspamd/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:edge
+FROM alpine:3.7
 
 RUN apk add --no-cache python py-jinja2 rspamd rspamd-controller rspamd-proxy ca-certificates