diff --git a/Dockerfile.bird_exporter b/Dockerfile.bird_exporter
index 0cf6358..46a4fa6 100644
--- a/Dockerfile.bird_exporter
+++ b/Dockerfile.bird_exporter
@@ -1,7 +1,9 @@
 FROM golang as builder
 
+ENV BIRD_EXPORTER_VERSION 1.4.1
+
 WORKDIR /go/
-RUN git clone -b 1.4.1 https://github.com/czerwonk/bird_exporter.git
+RUN git clone -b $BIRD_EXPORTER_VERSION https://github.com/czerwonk/bird_exporter.git
 
 WORKDIR /go/bird_exporter
 RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o /go/bin/bird_exporter