diff --git a/Dockerfile b/Dockerfile
index ac8b4f199..cc9ec311b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,7 @@ MAINTAINER Thomas Boerger <thomas@webhippie.de>
 
 EXPOSE 22 3000
 
-RUN apk -U --no-cache add \
+RUN apk --no-cache add \
     su-exec \
     ca-certificates \
     sqlite \
diff --git a/Dockerfile.aarch64 b/Dockerfile.aarch64
index 34598332f..9f91ae90b 100644
--- a/Dockerfile.aarch64
+++ b/Dockerfile.aarch64
@@ -2,7 +2,7 @@ FROM multiarch/alpine:aarch64-v3.5
 
 EXPOSE 22 3000
 
-RUN apk -U --no-cache add \
+RUN apk --no-cache add \
     su-exec \
     ca-certificates \
     sqlite \
diff --git a/Dockerfile.rpi b/Dockerfile.rpi
index 23b9f130b..10bd4437d 100644
--- a/Dockerfile.rpi
+++ b/Dockerfile.rpi
@@ -3,7 +3,7 @@ MAINTAINER Thomas Boerger <thomas@webhippie.de>
 
 EXPOSE 22 3000
 
-RUN apk -U --no-cache add \
+RUN apk --no-cache add \
     su-exec \
     ca-certificates \
     sqlite \