diff --git a/lib/bkctld-check b/lib/bkctld-check
index 254b86f..ec32a2a 100755
--- a/lib/bkctld-check
+++ b/lib/bkctld-check
@@ -14,6 +14,8 @@ nb_ok=0
 nb_unkn=0
 output=""
 
+# Check if the backup disk is properly mounted
+
 if [ -b "${BACKUP_DISK}" ]; then
     # If backup disk is encrypted, verify that it's open
     cryptsetup isLuks "${BACKUP_DISK}"
@@ -35,14 +37,20 @@ if [ -b "${BACKUP_DISK}" ]; then
     fi
 fi
 
-read_variable() {
-    var_name=$1
-    file=$2
+# Check if the firewall file is sourced
 
-    pattern="^\s*${var_name}=-?[0-9]+"
+minifirewall_config=/etc/default/minifirewall
 
-    grep --extended-regexp --only-matching "${pattern}" "${file}" | cut -d= -f2
-}
+if [ -n "${FIREWALL_RULES}" ] \
+&& [ -r "${FIREWALL_RULES}" ] \
+&& [ -f "${minifirewall_config}" ]; then
+    if ! grep -qE "^(\.|source) ${FIREWALL_RULES}" "${minifirewall_config}"; then
+        echo "Firewall file '${FIREWALL_RULES}' doesn't seem to be sourced by '${minifirewall_config}'."
+        exit 2
+    fi
+fi
+
+# Check each jail status
 
 check_jail() {
     jail_name=$1
@@ -55,8 +63,8 @@ check_jail() {
     check_policy_file=$(current_jail_check_policy_file "${jail_name}")
 
     if [ -f "${check_policy_file}" ]; then
-        local_critical=$(read_variable "CRITICAL" "${check_policy_file}")
-        local_warning=$(read_variable "WARNING" "${check_policy_file}")
+        local_critical=$(read_variable "${check_policy_file}" "CRITICAL")
+        local_warning=$(read_variable "${check_policy_file}" "WARNING")
     else
         unset local_critical
         unset local_warning
diff --git a/lib/includes b/lib/includes
index adc4691..86608c2 100755
--- a/lib/includes
+++ b/lib/includes
@@ -284,3 +284,12 @@ mount_jail_fs() {
     ln -fs "${jail_path}/proc/self/fd/2" "${jail_path}/dev/stderr"
     ln -fs "${jail_path}/proc/kcore" "${jail_path}/dev/core"
 }
+
+read_variable() {
+    file=${1:?}
+    var_name=${2:?}
+
+    pattern="^\s*${var_name}=-?[0-9]+"
+
+    grep --extended-regexp --only-matching "${pattern}" "${file}" | cut -d= -f2
+}
diff --git a/test/checks.bats b/test/checks.bats
index bd102fa..524f7d6 100644
--- a/test/checks.bats
+++ b/test/checks.bats
@@ -134,3 +134,33 @@ OUT
     run /usr/lib/bkctld/bkctld-check
     assert_equal "2" "$status"
 }
+
+@test "Check CRITICAL if firewall rules are not sourced" {
+    firewall_rules_file="/etc/firewall.rc.jails"
+    set_variable "/etc/default/bkctld" "FIREWALL_RULES" "${firewall_rules_file}"
+    echo "" > "${firewall_rules_file}"
+
+    # Without sourcing
+    echo "" > "/etc/default/minifirewall"
+    # … the check should be "critical"
+    run /usr/lib/bkctld/bkctld-check
+    assert_equal "2" "$status"
+}
+
+@test "Check OK if firewall rules are sourced" {
+    firewall_rules_file="/etc/firewall.rc.jails"
+    set_variable "/etc/default/bkctld" "FIREWALL_RULES" "${firewall_rules_file}"
+    echo "" > "${firewall_rules_file}"
+
+    # Sourcing file with '.'
+    echo ". ${firewall_rules_file}" > "/etc/default/minifirewall"
+    # … the check should be "critical"
+    run /usr/lib/bkctld/bkctld-check
+    assert_equal "0" "$status"
+
+    # Sourcing file with 'source'
+    echo "source ${firewall_rules_file}" > "/etc/default/minifirewall"
+    # … the check should be "critical"
+    run /usr/lib/bkctld/bkctld-check
+    assert_equal "0" "$status"
+}
diff --git a/test/test_helper.bash b/test/test_helper.bash
index a640339..e1bf862 100644
--- a/test/test_helper.bash
+++ b/test/test_helper.bash
@@ -5,7 +5,7 @@ setup() {
     rm -f /root/bkctld.key*
     ssh-keygen -t rsa -N "" -f /root/bkctld.key -q
 
-    grep -qE "^BACKUP_DISK=" /etc/default/bkctld || echo "BACKUP_DISK=/dev/vdb" >> /etc/default/bkctld
+    set_variable "/etc/default/bkctld" "BACKUP_DISK" "/dev/vdb"
 
     JAILNAME=$(tr -cd '[:alnum:]' < /dev/urandom | fold -w15 | head -n1)
     JAILPATH="/backup/jails/${JAILNAME}"
@@ -17,9 +17,28 @@ setup() {
 }
 
 teardown() {
+    remove_variable "/etc/default/bkctld" "BACKUP_DISK"
     /usr/lib/bkctld/bkctld-remove "${JAILNAME}" && rm -rf "${INCSPATH}"
 }
 
+set_variable() {
+    file=${1:?}
+    var_name=${2:?}
+    var_value=${3:-}
+
+    if grep -qE "^\s*${var_name}=" "${file}"; then
+        sed -i "s|^\s*${var_name}=.*|${var_name}=${var_value}|" "${file}"
+    else
+        echo "${var_name}=${var_value}" >> "${file}"
+    fi
+}
+remove_variable() {
+    file=${1:?}
+    var_name=${2:?}
+
+    sed -i "s|^\s*${var_name}=.*|d" "${file}"
+}
+
 is_btrfs() {
     path=$1