diff --git a/Dockerfile b/Dockerfile
index a201180..51312d5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,6 +6,8 @@ RUN mkdir -p /app/code/nginx
 
 WORKDIR /app/code
 
+ENV MATRIXVERSION=v0.99.5.2
+
 EXPOSE 8000
 EXPOSE 3478/udp
 
@@ -32,7 +34,7 @@ RUN apt-get install -y build-essential python2.7-dev libffi-dev libldap2-dev lib
 RUN pip install --upgrade pip
 RUN pip install --upgrade setuptools
 RUN pip install psycopg2-binary py-bcrypt python-ldap matrix-synapse-ldap3 lxml netaddr twisted jinja2
-RUN pip install https://github.com/matrix-org/synapse/archive/v0.99.5.1.tar.gz
+RUN pip install https://github.com/matrix-org/synapse/archive/${MATRIXVERSION}.tar.gz
 #https://github.com/matrix-org/synapse/tarball/master
 
 # copy index.html