diff --git a/containers/xos/Dockerfile.devel b/containers/xos/Dockerfile.devel
index 2acc578..feae96a 100644
--- a/containers/xos/Dockerfile.devel
+++ b/containers/xos/Dockerfile.devel
@@ -99,7 +99,7 @@
 RUN git clone https://github.com/OpenVPN/easy-rsa.git /opt/openvpn
 RUN git -C /opt/openvpn pull origin master
 RUN cp /opt/xos/services/vpn/vars /opt/openvpn/vars
-RUN source /opt/openvpn/vars
+RUN . /opt/openvpn/vars
 RUN /opt/openvpn/clean-all
 RUN /opt/openvpn/build-ca --batch
 RUN /opt/openvpn/build-key-server --batch server