diff --git a/Dockerfile b/Dockerfile
index 0e535c9..73ace59 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ ARG EMAIL=monit@sutty.nl
 FROM alpine:${ALPINE_VERSION} AS build
 ARG RUBY_VERSION=2.7
 ARG RUBY_PATCH=5
-ENV EMAIL ${EMAIL:-monit@sutty.nl}
+ENV EMAIL=${EMAIL:-monit@sutty.nl}
 
 RUN apk add --no-cache ruby~${RUBY_VERSION}.${RUBY_PATCH} patch