diff --git a/ci/docker/Dockerfile.ruby b/ci/docker/Dockerfile.ruby
index a1dccdddb5..81e6497d1c 100644
--- a/ci/docker/Dockerfile.ruby
+++ b/ci/docker/Dockerfile.ruby
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.12.3
 
 ARG JENKINS_UID=1000
 RUN adduser -D -S -u ${JENKINS_UID} jenkins
diff --git a/ci/docker/Dockerfile.sbt b/ci/docker/Dockerfile.sbt
index 56273adc83..dd3aab7b6e 100644
--- a/ci/docker/Dockerfile.sbt
+++ b/ci/docker/Dockerfile.sbt
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.12.3
 
 ENV SCALA_VERSION 2.11.7
 ENV SBT_VERSION 0.13.9