diff --git a/docker/Dockerfile b/docker/Dockerfile
index 561856b..0171e95 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,5 +1,5 @@
 # Start with BioSim base image.
-ARG BASE_IMAGE=latest
+ARG BASE_IMAGE=latest@sha256:5eb67b09e3fdf64b3128bd9501e08a0cbb007804b678f2096728d8c1260e6217
 FROM ghcr.io/ccpbiosim/jupyterhub-base:$BASE_IMAGE
 
 LABEL maintainer="James Gebbie-Rayet <james.gebbie@stfc.ac.uk>"