diff --git a/prog/weave-npc/Dockerfile b/prog/weave-npc/Dockerfile
index 86e366a7..711c7eca 100644
--- a/prog/weave-npc/Dockerfile
+++ b/prog/weave-npc/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.4
 
 LABEL maintainer "Weaveworks Inc <help@weave.works>"
 LABEL works.weave.role=system \
diff --git a/prog/weaveexec/Dockerfile b/prog/weaveexec/Dockerfile
index b490d8df..abb1d29f 100644
--- a/prog/weaveexec/Dockerfile
+++ b/prog/weaveexec/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.4
 
 LABEL maintainer "Weaveworks Inc <help@weave.works>"
 LABEL works.weave.role=system \