diff --git a/Dockerfile b/Dockerfile
index 45e4311..18ea32b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.8-alpine as builder
+FROM golang:1.9-alpine as builder
 ADD . /go/src/github.com/jimeh/casecmp
 WORKDIR /go/src/github.com/jimeh/casecmp
 RUN CGO_ENABLED=0 go build -a -o /casecmp \
@@ -6,6 +6,7 @@ RUN CGO_ENABLED=0 go build -a -o /casecmp \
 
 FROM scratch
 COPY --from=builder /casecmp /
+ENV PORT 8080
 EXPOSE 8080
 WORKDIR /
-CMD ["/casecmp", "--port", "8080"]
+CMD ["/casecmp"]