diff --git a/data/helpers.d/backend b/data/helpers.d/backend
index 12e2b1964..2109b17ca 100644
--- a/data/helpers.d/backend
+++ b/data/helpers.d/backend
@@ -16,6 +16,7 @@
 # Unless you use the option --non-append
 ynh_use_logrotate () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=lnuya
 	declare -Ar args_array=( [l]=logfile= [n]=nonappend [u]=specific_user= [y]=non [a]=append )
 	# [y]=non [a]=append are only for legacy purpose, to not fail on the old option '--non-append'
 	local logfile
@@ -113,6 +114,7 @@ ynh_remove_logrotate () {
 #
 ynh_add_systemd_config () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=st
 	declare -Ar args_array=( [s]=service= [t]=template= )
 	local service
 	local template
@@ -147,6 +149,7 @@ ynh_add_systemd_config () {
 #
 ynh_remove_systemd_config () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=s
 	declare -Ar args_array=( [s]=service= )
 	local service
 	# Manage arguments with getopts
diff --git a/data/helpers.d/filesystem b/data/helpers.d/filesystem
index 55bad87e8..2e9f93166 100644
--- a/data/helpers.d/filesystem
+++ b/data/helpers.d/filesystem
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 CAN_BIND=${CAN_BIND:-1}
 
 # Add a file or a directory to the list of paths to backup
@@ -46,6 +48,7 @@ ynh_backup() {
     # TODO find a way to avoid injection by file strange naming !
 
     # Declare an array to define the options of this helper.
+    local legacy_args=sdbm
     declare -Ar args_array=( [s]=src_path= [d]=dest_path= [b]=is_big [m]=not_mandatory )
     local src_path
     local dest_path
@@ -214,6 +217,7 @@ with open(sys.argv[1], 'r') as backup_file:
 #
 ynh_restore_file () {
     # Declare an array to define the options of this helper.
+    local legacy_args=odm
     declare -Ar args_array=( [o]=origin_path= [d]=dest_path= [m]=not_mandatory )
     local origin_path
     local archive_path
@@ -307,6 +311,7 @@ properly with chmod/chown." >&2
 # | arg: -f, --file - The file on which the checksum will performed, then stored.
 ynh_store_file_checksum () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=f
 	declare -Ar args_array=( [f]=file= )
 	local file
 	# Manage arguments with getopts
@@ -328,6 +333,7 @@ ynh_store_file_checksum () {
 # | ret: Return the name a the backup file, or nothing
 ynh_backup_if_checksum_is_different () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=f
 	declare -Ar args_array=( [f]=file= )
 	local file
 	# Manage arguments with getopts
@@ -356,6 +362,7 @@ ynh_backup_if_checksum_is_different () {
 # | arg: -f, --file= - The file for which the checksum will be deleted
 ynh_delete_file_checksum () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=f
 	declare -Ar args_array=( [f]=file= )
 	local file
 	# Manage arguments with getopts
@@ -371,6 +378,7 @@ ynh_delete_file_checksum () {
 # | arg: -f, --file - File or directory to remove
 ynh_secure_remove () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=f
 	declare -Ar args_array=( [f]=file= )
 	local file
 	# Manage arguments with getopts
diff --git a/data/helpers.d/getopts b/data/helpers.d/getopts
index b9897f7d9..e9fbe18e8 100644
--- a/data/helpers.d/getopts
+++ b/data/helpers.d/getopts
@@ -53,33 +53,33 @@ ynh_handle_getopts_args () {
 
 		# For each option in the array, reduce to short options for getopts (e.g. for [u]=user, --user will be -u)
 		# And built parameters string for getopts
-		# ${!args_array[@]} is the list of all keys in the array (A key is 'u' in [u]=user, user is a value)
+		# ${!args_array[@]} is the list of all option_flags in the array (An option_flag is 'u' in [u]=user, user is a value)
 		local getopts_parameters=""
-		local key=""
-		for key in "${!args_array[@]}"
+		local option_flag=""
+		for option_flag in "${!args_array[@]}"
 		do
-			# Concatenate each keys of the array to build the string of arguments for getopts
+			# Concatenate each option_flags of the array to build the string of arguments for getopts
 			# Will looks like 'abcd' for -a -b -c -d
-			# If the value of a key finish by =, it's an option with additionnal values. (e.g. --user bob or -u bob)
-			# Check the last character of the value associate to the key
-			if [ "${args_array[$key]: -1}" = "=" ]
+			# If the value of an option_flag finish by =, it's an option with additionnal values. (e.g. --user bob or -u bob)
+			# Check the last character of the value associate to the option_flag
+			if [ "${args_array[$option_flag]: -1}" = "=" ]
 			then
 				# For an option with additionnal values, add a ':' after the letter for getopts.
-				getopts_parameters="${getopts_parameters}${key}:"
+				getopts_parameters="${getopts_parameters}${option_flag}:"
 			else
-				getopts_parameters="${getopts_parameters}${key}"
+				getopts_parameters="${getopts_parameters}${option_flag}"
 			fi
 			# Check each argument given to the function
 			local arg=""
 			# ${#arguments[@]} is the size of the array
 			for arg in `seq 0 $(( ${#arguments[@]} - 1 ))`
 			do
-				# And replace long option (value of the key) by the short option, the key itself
+				# And replace long option (value of the option_flag) by the short option, the option_flag itself
 				# (e.g. for [u]=user, --user will be -u)
 				# Replace long option with =
-				arguments[arg]="${arguments[arg]//--${args_array[$key]}/-${key} }"
+				arguments[arg]="${arguments[arg]//--${args_array[$option_flag]}/-${option_flag} }"
 				# And long option without =
-				arguments[arg]="${arguments[arg]//--${args_array[$key]%=}/-${key}}"
+				arguments[arg]="${arguments[arg]//--${args_array[$option_flag]%=}/-${option_flag}}"
 			done
 		done
 
@@ -132,6 +132,7 @@ ynh_handle_getopts_args () {
 						# Declare the content of option_var as a variable.
 						eval ${option_var}=""
 						# Then read the array value per value
+						local i
 						for i in `seq 0 $(( ${#all_args[@]} - 1 ))`
 						do
 							# If this argument is an option, end here.
@@ -166,24 +167,27 @@ ynh_handle_getopts_args () {
 		if [ "${arguments[0]:0:1}" != "-" ]
 		then
 			# If not, enter in legacy mode and manage the arguments as positionnal ones.
-			echo "! Helper used in legacy mode !"
+			ynh_print_info --message="! Helper used in legacy mode !"
+			local i
 			for i in `seq 0 $(( ${#arguments[@]} -1 ))`
 			do
-				# Use getopts_parameters as a list of key of the array args_array
+				# Try to use legacy_args as a list of option_flag of the array args_array
+				# Otherwise, fallback to getopts_parameters to get the option_flag. But an associative arrays isn't always sorted in the correct order...
 				# Remove all ':' in getopts_parameters
-				getopts_parameters=${getopts_parameters//:}
-				# Get the key from getopts_parameters, by using the key according to the position of the argument.
-				key=${getopts_parameters:$i:1}
-				# Use the long option, corresponding to the key, as a variable
+				getopts_parameters=${legacy_args:-${getopts_parameters//:}}
+				# Get the option_flag from getopts_parameters, by using the option_flag according to the position of the argument.
+				option_flag=${getopts_parameters:$i:1}
+				# Use the long option, corresponding to the option_flag, as a variable
 				# (e.g. for [u]=user, 'user' will be used as a variable)
 				# Also, remove '=' at the end of the long option
 				# The variable name will be stored in 'option_var'
-				local option_var="${args_array[$key]%=}"
+				local option_var="${args_array[$option_flag]%=}"
 
 				# Store each value given as argument in the corresponding variable
 				# The values will be stored in the same order than $args_array
 				eval ${option_var}+=\"${arguments[$i]}\"
 			done
+			unset legacy_args
 		else
 			# END LEGACY MODE
 			# Call parse_arg and pass the modified list of args as an array of arguments.
diff --git a/data/helpers.d/ip b/data/helpers.d/ip
index 09c974782..c50d8be73 100644
--- a/data/helpers.d/ip
+++ b/data/helpers.d/ip
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Validate an IP address
 #
 # usage: ynh_validate_ip --family=family --ip_address=ip_address
@@ -10,6 +12,7 @@ ynh_validate_ip()
   # http://stackoverflow.com/questions/319279/how-to-validate-ip-address-in-python#319298
 
   # Declare an array to define the options of this helper.
+  local legacy_args=fi
   declare -Ar args_array=( [f]=family= [i]=ip_address= )
   local family
   local ip_address
@@ -40,6 +43,7 @@ EOF
 ynh_validate_ip4()
 {
   # Declare an array to define the options of this helper.
+  local legacy_args=i
   declare -Ar args_array=( [i]=ip_address= )
   local ip_address
   # Manage arguments with getopts
@@ -59,6 +63,7 @@ ynh_validate_ip4()
 ynh_validate_ip6()
 {
   # Declare an array to define the options of this helper.
+  local legacy_args=i
   declare -Ar args_array=( [i]=ip_address= )
   local ip_address
   # Manage arguments with getopts
diff --git a/data/helpers.d/mysql b/data/helpers.d/mysql
index 4898bed92..538b00469 100644
--- a/data/helpers.d/mysql
+++ b/data/helpers.d/mysql
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 MYSQL_ROOT_PWD_FILE=/etc/yunohost/mysql
 
 # Open a connection as a user
@@ -11,6 +13,7 @@ MYSQL_ROOT_PWD_FILE=/etc/yunohost/mysql
 # | arg: -d, --database - the database to connect to
 ynh_mysql_connect_as() {
     # Declare an array to define the options of this helper.
+    local legacy_args=upd
     declare -Ar args_array=( [u]=user= [p]=password= [d]=database= )
     local user
     local password
@@ -29,6 +32,7 @@ ynh_mysql_connect_as() {
 # | arg: -d, --database - the database to connect to
 ynh_mysql_execute_as_root() {
     # Declare an array to define the options of this helper.
+    local legacy_args=sd
     declare -Ar args_array=( [s]=sql= [d]=database= )
     local sql
     local database
@@ -47,6 +51,7 @@ ynh_mysql_execute_as_root() {
 # | arg: -d, --database - the database to connect to
 ynh_mysql_execute_file_as_root() {
     # Declare an array to define the options of this helper.
+    local legacy_args=fd
     declare -Ar args_array=( [f]=file= [d]=database= )
     local file
     local database
@@ -103,6 +108,7 @@ ynh_mysql_drop_db() {
 # | ret: the mysqldump output
 ynh_mysql_dump_db() {
     # Declare an array to define the options of this helper.
+    local legacy_args=d
     declare -Ar args_array=( [d]=database= )
     local database
     # Manage arguments with getopts
@@ -130,6 +136,7 @@ ynh_mysql_create_user() {
 ynh_mysql_user_exists()
 {
    # Declare an array to define the options of this helper.
+   local legacy_args=u
    declare -Ar args_array=( [u]=user= )
    local user
    # Manage arguments with getopts
@@ -164,6 +171,7 @@ ynh_mysql_drop_user() {
 # | arg: -p, --db_password - Password of the database. If not given, a password will be generated
 ynh_mysql_setup_db () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=unp
 	declare -Ar args_array=( [u]=db_user= [n]=db_name= [p]=db_password= )
 	local db_user
 	local db_name
@@ -186,6 +194,7 @@ ynh_mysql_setup_db () {
 # | arg: -n, --db_name - Name of the database
 ynh_mysql_remove_db () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=un
 	declare -Ar args_array=( [u]=db_user= [n]=db_name= )
 	local db_user
 	local db_name
@@ -216,6 +225,7 @@ ynh_mysql_remove_db () {
 # | ret: the corrected name
 ynh_sanitize_dbid () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=n
 	declare -Ar args_array=( [n]=db_name= )
 	local db_name
 	# Manage arguments with getopts
diff --git a/data/helpers.d/network b/data/helpers.d/network
index 0059702e9..a765d6346 100644
--- a/data/helpers.d/network
+++ b/data/helpers.d/network
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Normalize the url path syntax
 # Handle the slash at the beginning of path and its absence at ending
 # Return a normalized url path
@@ -12,6 +14,7 @@
 # | arg: -p, --path_url - URL path to normalize before using it
 ynh_normalize_url_path () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=p
 	declare -Ar args_array=( [p]=path_url= )
 	local path_url
 	# Manage arguments with getopts
@@ -35,6 +38,7 @@ ynh_normalize_url_path () {
 # | arg: -p, --port - port to start to search
 ynh_find_port () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=p
 	declare -Ar args_array=( [p]=port= )
 	local port
 	# Manage arguments with getopts
@@ -57,6 +61,7 @@ ynh_find_port () {
 # | arg: -p, --path_url - the web path to check the availability of
 ynh_webpath_available () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=dp
 	declare -Ar args_array=( [d]=domain= [p]=path_url= )
 	local domain
 	local path_url
@@ -76,6 +81,7 @@ ynh_webpath_available () {
 # | arg: -p, --path_url - the web path to be registered
 ynh_webpath_register () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=adp
 	declare -Ar args_array=( [a]=app= [d]=domain= [p]=path_url= )
 	local app
 	local domain
diff --git a/data/helpers.d/nodejs b/data/helpers.d/nodejs
index fcba2d75a..c4332b60c 100644
--- a/data/helpers.d/nodejs
+++ b/data/helpers.d/nodejs
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 n_install_dir="/opt/node_n"
 node_version_path="$n_install_dir/n/versions/node"
 # N_PREFIX is the directory of n, it needs to be loaded as a environment variable.
@@ -61,6 +63,7 @@ ynh_install_nodejs () {
 	# Use n, https://github.com/tj/n to manage the nodejs versions
 
 	# Declare an array to define the options of this helper.
+	local legacy_args=n
 	declare -Ar args_array=( [n]=nodejs_version= )
 	local nodejs_version
 	# Manage arguments with getopts
diff --git a/data/helpers.d/package b/data/helpers.d/package
index 820a61ef4..485cee957 100644
--- a/data/helpers.d/package
+++ b/data/helpers.d/package
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Check if apt is free to use, or wait, until timeout.
 #
 # [internal]
@@ -29,6 +31,7 @@ ynh_wait_dpkg_free() {
 # | arg: -p, --package - the package name to check
 ynh_package_is_installed() {
     # Declare an array to define the options of this helper.
+    local legacy_args=p
     declare -Ar args_array=( [p]=package= )
     local package
     # Manage arguments with getopts
@@ -48,6 +51,7 @@ ynh_package_is_installed() {
 # | ret: the version or an empty string
 ynh_package_version() {
     # Declare an array to define the options of this helper.
+    local legacy_args=p
     declare -Ar args_array=( [p]=package= )
     local package
     # Manage arguments with getopts
diff --git a/data/helpers.d/print b/data/helpers.d/print
index e605e7e4a..353fa595d 100644
--- a/data/helpers.d/print
+++ b/data/helpers.d/print
@@ -1,7 +1,10 @@
+#!/bin/bash
+
 # Print a message to stderr and exit
 # usage: ynh_die --message=MSG [--ret_code=RETCODE]
 ynh_die() {
   # Declare an array to define the options of this helper.
+  local legacy_args=mc
   declare -Ar args_array=( [m]=message= [c]=ret_code= )
   local message
   local ret_code
@@ -17,6 +20,7 @@ ynh_die() {
 # usage: ynh_print_info --message="Some message"
 ynh_print_info() {
     # Declare an array to define the options of this helper.
+    local legacy_args=m
     declare -Ar args_array=( [m]=message= )
     local message
     # Manage arguments with getopts
@@ -56,6 +60,7 @@ ynh_print_log () {
 # | arg: -m, --message - The text to print
 ynh_print_warn () {
   # Declare an array to define the options of this helper.
+  local legacy_args=m
   declare -Ar args_array=( [m]=message= )
   local message
   # Manage arguments with getopts
@@ -70,6 +75,7 @@ ynh_print_warn () {
 # | arg: -m, --message - The text to print
 ynh_print_err () {
   # Declare an array to define the options of this helper.
+  local legacy_args=m
   declare -Ar args_array=( [m]=message= )
   local message
   # Manage arguments with getopts
diff --git a/data/helpers.d/setting b/data/helpers.d/setting
index 29eeecd3c..6f75f6c80 100644
--- a/data/helpers.d/setting
+++ b/data/helpers.d/setting
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Get an application setting
 #
 # usage: ynh_app_setting_get --app=app --key=key
@@ -5,6 +7,7 @@
 # | arg: -k, --key - the setting to get
 ynh_app_setting_get() {
     # Declare an array to define the options of this helper.
+    local legacy_args=ak
     declare -Ar args_array=( [a]=app= [k]=key= )
     local app
     local key
@@ -22,6 +25,7 @@ ynh_app_setting_get() {
 # | arg: -v, --value - the setting value to set
 ynh_app_setting_set() {
     # Declare an array to define the options of this helper.
+    local legacy_args=akv
     declare -Ar args_array=( [a]=app= [k]=key= [v]=value= )
     local app
     local key
@@ -39,6 +43,7 @@ ynh_app_setting_set() {
 # | arg: -k, --key - the setting to delete
 ynh_app_setting_delete() {
     # Declare an array to define the options of this helper.
+    local legacy_args=ak
     declare -Ar args_array=( [a]=app= [k]=key= )
     local app
     local key
diff --git a/data/helpers.d/string b/data/helpers.d/string
index b4dfb596d..739757d43 100644
--- a/data/helpers.d/string
+++ b/data/helpers.d/string
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Generate a random string
 #
 # example: pwd=$(ynh_string_random --length=8)
@@ -6,6 +8,7 @@
 # | arg: -l, --length - the string length to generate (default: 24)
 ynh_string_random() {
     # Declare an array to define the options of this helper.
+    local legacy_args=l
     declare -Ar args_array=( [l]=length= )
     local length
     # Manage arguments with getopts
@@ -29,6 +32,7 @@ ynh_string_random() {
 # (see sed manual page for more information)
 ynh_replace_string () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=mrf
 	declare -Ar args_array=( [m]=match_string= [r]=replace_string= [f]=target_file= )
 	local match_string
 	local replace_string
@@ -55,6 +59,7 @@ ynh_replace_string () {
 # characters, you can't use some regular expressions and sub-expressions.
 ynh_replace_special_string () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=mrf
 	declare -Ar args_array=( [m]=match_string= [r]=replace_string= [f]=target_file= )
 	local match_string
 	local replace_string
diff --git a/data/helpers.d/system b/data/helpers.d/system
index 70cc57493..968135f16 100644
--- a/data/helpers.d/system
+++ b/data/helpers.d/system
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Manage a fail of the script
 #
 # [internal]
diff --git a/data/helpers.d/user b/data/helpers.d/user
index 3947ebe7f..1fa8f3f79 100644
--- a/data/helpers.d/user
+++ b/data/helpers.d/user
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Check if a YunoHost user exists
 #
 # example: ynh_user_exists 'toto' || exit 1
@@ -6,6 +8,7 @@
 # | arg: -u, --username - the username to check
 ynh_user_exists() {
     # Declare an array to define the options of this helper.
+    local legacy_args=u
     declare -Ar args_array=( [u]=username= )
     local username
     # Manage arguments with getopts
@@ -24,6 +27,7 @@ ynh_user_exists() {
 # | ret: string - the key's value
 ynh_user_get_info() {
     # Declare an array to define the options of this helper.
+    local legacy_args=uk
     declare -Ar args_array=( [u]=username= [k]=key= )
     local username
     local key
@@ -50,6 +54,7 @@ ynh_user_list() {
 # | arg: -u, --username - the username to check
 ynh_system_user_exists() {
     # Declare an array to define the options of this helper.
+    local legacy_args=u
     declare -Ar args_array=( [u]=username= )
     local username
     # Manage arguments with getopts
@@ -65,6 +70,7 @@ ynh_system_user_exists() {
 # | arg: -h, --home_dir - Path of the home dir for the user. Usually the final path of the app. If this argument is omitted, the user will be created without home
 ynh_system_user_create () {
 	# Declare an array to define the options of this helper.
+	local legacy_args=uh
 	declare -Ar args_array=( [u]=username= [h]=home_dir= )
 	local username
 	local home_dir
@@ -88,6 +94,7 @@ ynh_system_user_create () {
 # | arg: -u, --username - Name of the system user that will be create
 ynh_system_user_delete () {
     # Declare an array to define the options of this helper.
+    local legacy_args=u
     declare -Ar args_array=( [u]=username= )
     local username
     # Manage arguments with getopts
diff --git a/data/helpers.d/utils b/data/helpers.d/utils
index 1488289fa..60ba709ba 100644
--- a/data/helpers.d/utils
+++ b/data/helpers.d/utils
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 # Extract a key from a plain command output
 #
 # example: yunohost user info tata --output-as plain | ynh_get_plain_key mail
@@ -146,6 +148,7 @@ ynh_backup_before_upgrade () {
 # | arg: -s, --source_id - Name of the app, if the package contains more than one app
 ynh_setup_source () {
     # Declare an array to define the options of this helper.
+    local legacy_args=ds
     declare -Ar args_array=( [d]=dest_dir= [s]=source_id= )
     local dest_dir
     local source_id