diff --git a/docker/RO/Dockerfile b/docker/RO/Dockerfile
index ba7d54d..04f7c4c 100644
--- a/docker/RO/Dockerfile
+++ b/docker/RO/Dockerfile
@@ -81,7 +81,8 @@
 FROM ubuntu:18.04
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
-    DEBIAN_FRONTEND=noninteractive apt-get --yes install python3-minimal=3.6.*
+    DEBIAN_FRONTEND=noninteractive apt-get --yes install python3-minimal=3.6.* \
+    && rm -rf /var/lib/apt/lists/*
 
 COPY --from=INSTALL /usr/lib/python3/dist-packages /usr/lib/python3/dist-packages
 COPY --from=INSTALL /usr/local/lib/python3.6/dist-packages  /usr/local/lib/python3.6/dist-packages