diff --git a/setup/firstuser.sh b/setup/firstuser.sh
index 540c565f..8d254b53 100644
--- a/setup/firstuser.sh
+++ b/setup/firstuser.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # If there aren't any mail users yet, create one.
 if [ -z "$(management/cli.py user)" ]; then
 	# The outut of "management/cli.py user" is a list of mail users. If there
diff --git a/setup/functions.sh b/setup/functions.sh
index 8e8b79e2..5a153d2a 100644
--- a/setup/functions.sh
+++ b/setup/functions.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # Turn on "strict mode." See http://redsymbol.net/articles/unofficial-bash-strict-mode/.
 # -e: exit if any command unexpectedly fails.
 # -u: exit if we have a variable typo.
diff --git a/setup/network-checks.sh b/setup/network-checks.sh
index 5d5351c7..16b9a175 100644
--- a/setup/network-checks.sh
+++ b/setup/network-checks.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # Install the 'host', 'sed', and and 'nc' tools. This script is run before
 # the rest of the system setup so we may not yet have things installed.
 apt_get_quiet install bind9-host sed netcat-openbsd
diff --git a/setup/questions.sh b/setup/questions.sh
index e7803363..2144d51f 100644
--- a/setup/questions.sh
+++ b/setup/questions.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 if [ -z "${NONINTERACTIVE:-}" ]; then
 	# Install 'dialog' so we can ask the user questions. The original motivation for
 	# this was being able to ask the user for input even if stdin has been redirected,
diff --git a/setup/system.sh b/setup/system.sh
index b4d1ae27..59a3fe8e 100755
--- a/setup/system.sh
+++ b/setup/system.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 source /etc/mailinabox.conf
 source setup/functions.sh # load our functions
 
diff --git a/tools/archive_conf_files.sh b/tools/archive_conf_files.sh
index 6efbccd5..d2ec2c9a 100644
--- a/tools/archive_conf_files.sh
+++ b/tools/archive_conf_files.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # Use this script to make an archive of the contents of all
 # of the configuration files we edit with editconf.py.
 for fn in $(grep -hr editconf.py setup | sed "s/tools\/editconf.py //" | sed "s/ .*//" | sort | uniq); do