diff --git a/Dockerfile b/Dockerfile
index 1ff28cb..3bf14b5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,6 +2,8 @@ FROM docker
 
 ENV SLEEP_TIME='5m'
 
+RUN apk add --update --no-cache bash
+
 COPY shepherd /usr/local/bin/shepherd
 
 ENTRYPOINT ["/usr/local/bin/shepherd"]
diff --git a/README.md b/README.md
index 1c3ee45..16780fe 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,7 @@ A Docker swarm service for automatically updating your services whenever their b
                           --replicas 1 \
                           --constraint "node.role==manager" \
                           --env SLEEP_TIME="5m" \
+                          --env BLACKLIST_SERVICES="shepherd" \
                           --mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock,ro \
                           mazzolino/shepherd
 
diff --git a/shepherd b/shepherd
index 585434d..5670de7 100755
--- a/shepherd
+++ b/shepherd
@@ -1,21 +1,27 @@
-#!/bin/ash
-# shellcheck shell=dash
+#!/bin/bash
 set -euo pipefail
 
 update_services() {
+  local blacklist="$1"
+
   for service in $(IFS="\n" docker service ls --quiet); do
     local name image_with_digest image
     name="$(docker service inspect "$service" -f '{{.Spec.Name}}')"
-    image_with_digest="$(docker service inspect "$service" -f '{{.Spec.TaskTemplate.ContainerSpec.Image}}')"
-    image=$(echo "$image_with_digest" | cut -d@ -f1)
-    echo "Updating service $name with image $image"
-    docker service update "$service" --image="$image" > /dev/null
+    if [[ " $blacklist " != *" $name "* ]]; then
+      image_with_digest="$(docker service inspect "$service" -f '{{.Spec.TaskTemplate.ContainerSpec.Image}}')"
+      image=$(echo "$image_with_digest" | cut -d@ -f1)
+      echo "Updating service $name with image $image"
+      docker service update "$service" --image="$image" > /dev/null
+    fi
   done
 }
 
 main() {
+  local blacklist="${BLACKLIST_SERVICES:-}"
+  [[ "$blacklist" != "" ]] && echo "Excluding services: $blacklist"
+
   while true; do
-    update_services
+    update_services "${blacklist}"
     echo "Sleeping ${SLEEP_TIME} before next update"
     sleep "${SLEEP_TIME}"
   done