diff --git a/Dockerfile b/Dockerfile
index af32ad7..7ff0b16 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,7 @@ ARG BASE_IMAGE=gitea.nulo.in/sutty/monit
 FROM ${BASE_IMAGE}:${ALPINE_VERSION}
 MAINTAINER "f <f@sutty.nl>"
 ARG KNOT_VERSION=3.1.8
-ENV SUTTYNS_FLAGS
+ENV SUTTYNS_FLAGS=""
 
 RUN apk add --no-cache knot~${KNOT_VERSION} suttyns
 COPY ./monit.conf /etc/monit.d/knot.conf