diff --git a/docker_push.sh b/docker_push.sh
index e064f55369d171f1b5f5a3716d48d4bd5305afc2..7fa7eedb67fb82e7370b9dfe03c1e45b78bd0db7 100755
--- a/docker_push.sh
+++ b/docker_push.sh
@@ -27,6 +27,6 @@ else
 fi
 
 $CAPTAIN push --branch-tags=false --commit-tags=true portal-backend
-cat $WORKSPACE/docker/runner/slack.json | sed "s/USER/${USER^}/" > $WORKSPACE/target/slack.json
+sed "s/USER/${USER^}/" $WORKSPACE/docker/runner/slack.json > $WORKSPACE/target/slack.json
 curl -k -X POST --data-urlencode payload@$WORKSPACE/target/slack.json https://hbps1.chuv.ch/slack/dev-activity
 rm -f $WORKSPACE/target/slack.json