diff --git a/setup.sh b/setup.sh
index e0dd8aef..a82b256e 100755
--- a/setup.sh
+++ b/setup.sh
@@ -19,11 +19,11 @@ USE_SELINUX=
 USE_TTY=
 VOLUME=
 
-RED="\e[31m\e[1m"
-WHITE="\e[37m"
-ORANGE="\e[38;5;214m"
-LBLUE="\e[94m"
-RESET="\e[0m"
+RED=$(echo -ne '\e[31m\e[1m')
+WHITE=$(echo -ne '\e[37m')
+ORANGE=$(echo -ne '\e[38;5;214m')
+LBLUE=$(echo -ne '\e[94m')
+RESET=$(echo -ne '\e[0m')
 
 set -euEo pipefail
 shopt -s inherit_errexit 2>/dev/null || true
@@ -47,7 +47,7 @@ function __err
 function _show_local_usage
 {
   # shellcheck disable=SC2059
-  printf "${ORANGE}OPTIONS${RESET}
+  printf '%s' "${ORANGE}OPTIONS${RESET}
     ${LBLUE}Config path, container or image adjustments${RESET}
         -i IMAGE_NAME
             Provides the name of the 'docker-mailserver' image. The default value is
@@ -78,7 +78,7 @@ function _show_local_usage
   [[ ${1:-} == 'no-exit' ]] && return 0
 
   # shellcheck disable=SC2059
-  printf "${ORANGE}EXIT STATUS${RESET}
+  printf '%s' "${ORANGE}EXIT STATUS${RESET}
     Exit status is 0 if the command was successful. If there was an unexpected error, an error
     message is shown describing the error. In case of an error, the script will exit with exit
     status 1.
@@ -231,7 +231,7 @@ function _main
     _run_in_new_container setup "${@}"
   fi
 
-  [[ ${1} == 'help' ]] && _show_local_usage
+  [[ ${1:-} == 'help' ]] && _show_local_usage
 
   return 0
 }
diff --git a/target/scripts/startup/setup-stack.sh b/target/scripts/startup/setup-stack.sh
index d6e7159d..56979936 100644
--- a/target/scripts/startup/setup-stack.sh
+++ b/target/scripts/startup/setup-stack.sh
@@ -155,7 +155,7 @@ function _setup_dovecot
 
   if ! grep -q -E '^stats_writer_socket_path=' /etc/dovecot/dovecot.conf
   then
-    printf '\nstats_writer_socket_path=\n' >>/etc/dovecot/dovecot.conf
+    printf '\n%s\n' 'stats_writer_socket_path=' >>/etc/dovecot/dovecot.conf
   fi
 
   # set mail_location according to mailbox format
diff --git a/test/mail_ssl_manual.bats b/test/mail_ssl_manual.bats
index 81e326a0..287734cf 100644
--- a/test/mail_ssl_manual.bats
+++ b/test/mail_ssl_manual.bats
@@ -99,7 +99,7 @@ function teardown_file() {
 }
 
 @test "checking ssl: manual cert changes are picked up by check-for-changes" {
-    printf 'someThingsChangedHere' \
+    printf '%s' 'someThingsChangedHere' \
       >>"$(pwd)/test/test-files/ssl/${DOMAIN_SSL_MANUAL}/with_ca/ecdsa/key.ecdsa.pem"
 
     run timeout 15 docker exec mail_manual_ssl bash -c "tail -F /var/log/supervisor/changedetector.log | sed '/Manual certificates have changed/ q'"