diff --git a/api_auth_docker/Dockerfile b/api_auth_docker/Dockerfile
index 33f0f87..ef25e78 100644
--- a/api_auth_docker/Dockerfile
+++ b/api_auth_docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM nginx:alpine
+FROM nginx:alpine # should be 3.8
 
 RUN apk add --update --no-cache \
 		bash \
diff --git a/cron_docker/Dockerfile b/cron_docker/Dockerfile
index 1a3b755..44eb442 100644
--- a/cron_docker/Dockerfile
+++ b/cron_docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.8
 
 RUN apk add --update --no-cache \
     curl
diff --git a/proxy_docker/Dockerfile b/proxy_docker/Dockerfile
index 9714944..faf086b 100644
--- a/proxy_docker/Dockerfile
+++ b/proxy_docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.8
 
 ENV HOME /proxy