diff --git a/deployment/docker/base/Dockerfile b/deployment/docker/base/Dockerfile
index 16f42fd77..59f3a20ef 100644
--- a/deployment/docker/base/Dockerfile
+++ b/deployment/docker/base/Dockerfile
@@ -1,6 +1,6 @@
 # See https://medium.com/on-docker/use-multi-stage-builds-to-inject-ca-certs-ad1e8f01de1b
 ARG certs_image=non-existing
-ARG root_image==non-existing
+ARG root_image=non-existing
 FROM $certs_image AS certs
 
 RUN apk update && apk upgrade && apk --update --no-cache add ca-certificates