diff --git a/dodona-java21.dockerfile b/dodona-java21.dockerfile
index 8e8b8b5..5829cc0 100644
--- a/dodona-java21.dockerfile
+++ b/dodona-java21.dockerfile
@@ -1,7 +1,7 @@
 FROM eclipse-temurin:21-jdk-alpine
 
 # Install jq for json querying in bash
-RUN apk add --update-cache jq \
+RUN apk add --no-cache jq=1.7.1-r0 \
  # Make sure the students can't find our secret path, which is mounted in
  # /mnt with a secure random name.
  && chmod 711 /mnt \