diff --git a/controllers/nginx/rootfs/Dockerfile b/controllers/nginx/rootfs/Dockerfile
index 6959d6bbc..b5fceb7e7 100644
--- a/controllers/nginx/rootfs/Dockerfile
+++ b/controllers/nginx/rootfs/Dockerfile
@@ -14,7 +14,9 @@
 
 FROM gcr.io/google_containers/nginx-slim:0.14
 
-RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y \
+RUN export DEBIAN_FRONTEND=noninteractive \
+  && apt-get update \
+  && apt-get install -y \
   diffutils \
   ssl-cert \
   --no-install-recommends \