diff --git a/Dockerfile b/Dockerfile
index 03010da..36198f1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,9 +1,11 @@
 FROM ubuntu:trusty
 
+ENV GUNICORN_WORKERS=4
+
 ADD . /httpbin
 
 RUN apt-get update -y && apt-get -y install python-pip && pip install gunicorn && pip install /httpbin
 
 EXPOSE 8080
 
-CMD ["gunicorn", "-w", "4", "-b", "0.0.0.0:8080", "httpbin:app"]
+CMD gunicorn -w "$GUNICORN_WORKERS" -b 0.0.0.0:8080 httpbin:app