diff --git a/docker/my_example.Dockerfile b/docker/my_example.Dockerfile
index 757dfa3..b77f260 100644
--- a/docker/my_example.Dockerfile
+++ b/docker/my_example.Dockerfile
@@ -11,9 +11,12 @@ FROM osrf/ros:${ROS_DISTRO}-desktop as base
 
 SHELL ["/bin/bash", "-c"] # change shell to bash because of better compatibility (standard shell would be sh otherwise).
 
+ENV UNDERLAY_WS=${UNDERLAY_WS}
+ENV OVERLAY_WS=${OVERLAY_WS}
+
 # First checks
-RUN echo "Underlay WS:" && ${UNDERLAY_WS}
-RUN echo "Overlay WS:" && ${OVERLAY_WS}
+RUN echo "Underlay WS:" && $UNDERLAY_WS
+RUN echo "Overlay WS:" && $OVERLAY_WS
 
 # Create Colcon workspace with external dependencies
 RUN mkdir -p ${UNDERLAY_WS}/src