diff --git a/scripts/ynh_add_extra_apt_repos__3 b/scripts/ynh_add_extra_apt_repos__3
index 3276f00..ef9ba2d 100644
--- a/scripts/ynh_add_extra_apt_repos__3
+++ b/scripts/ynh_add_extra_apt_repos__3
@@ -27,7 +27,7 @@ ynh_pin_repo () {
 	name="${name:-$app}"
 	append=${append:-0}
 
-	if [ $append -eq 1 ]
+	if [ "$append" -eq 1 ]
 	then
 		append="tee -a"
 	else
@@ -128,7 +128,7 @@ ynh_install_extra_repo () {
 	local component="${repo##$uri $suite }"
 
 	# Add the repository into sources.list.d
-	ynh_add_repo --uri="$uri" --suite="$suite" --component="$component" --name="$name" $append
+	ynh_add_repo --uri="$uri" --suite="$suite" --component="$component" --name="$name" "$append"
 
 	# Pin the new repo with the default priority, so it won't be used for upgrades.
 	# Build $pin from the uri without http and any sub path
@@ -139,13 +139,13 @@ ynh_install_extra_repo () {
 	then
 		priority="--priority=$priority"
 	fi
-	ynh_pin_repo --package="*" --pin="origin \"$pin\"" $priority --name="$name" $append
+	ynh_pin_repo --package="*" --pin="origin \"$pin\"" "$priority" --name="$name" "$append"
 
 	# Get the public key for the repo
 	if [ -n "$key" ]
 	then
 		mkdir -p "/etc/apt/trusted.gpg.d"
-		wget -q "$key" -O - | gpg --dearmor | $wget_append /etc/apt/trusted.gpg.d/$name.gpg > /dev/null
+		wget -q "$key" -O - | gpg --dearmor | $wget_append /etc/apt/trusted.gpg.d/"$name".gpg > /dev/null
 	fi
 
 	# Update the list of package with the new repo
@@ -200,13 +200,13 @@ ynh_install_extra_app_dependencies () {
 		key="--key=$key"
 	fi
 	# Add an extra repository for those packages
-	ynh_install_extra_repo --repo="$repo" $key --priority=995 --name=$name
+	ynh_install_extra_repo --repo="$repo" "$key" --priority=995 --name="$name"
 
 	# Install requested dependencies from this extra repository.
 	ynh_add_app_dependencies --package="$package"
 
 	# Remove this extra repository after packages are installed
-	ynh_remove_extra_repo --name=$app
+	ynh_remove_extra_repo --name="$app"
 }
 
 #=================================================
@@ -252,7 +252,7 @@ ynh_install_app_dependencies () {
         dependencies="$(echo "$dependencies" | sed 's/\([^(\<=\>]\)\([\<=\>]\+\)\([^,]\+\)/\1 (\2 \3)/g')"
     fi
 
-    cat > /tmp/${dep_app}-ynh-deps.control << EOF	# Make a control file for equivs-build
+    cat > /tmp/"${dep_app}"-ynh-deps.control << EOF	# Make a control file for equivs-build
 Section: misc
 Priority: optional
 Package: ${dep_app}-ynh-deps
@@ -262,10 +262,10 @@ Architecture: all
 Description: Fake package for $app (YunoHost app) dependencies
  This meta-package is only responsible of installing its dependencies.
 EOF
-    ynh_package_install_from_equivs /tmp/${dep_app}-ynh-deps.control \
+    ynh_package_install_from_equivs /tmp/"${dep_app}"-ynh-deps.control \
         || ynh_die --message="Unable to install dependencies"	# Install the fake package and its dependencies
-    rm /tmp/${dep_app}-ynh-deps.control
-    ynh_app_setting_set --app=$app --key=apt_dependencies --value="$dependencies"
+    rm /tmp/"${dep_app}"-ynh-deps.control
+    ynh_app_setting_set --app="$app" --key=apt_dependencies --value="$dependencies"
 }
 
 ynh_add_app_dependencies () {
@@ -279,12 +279,12 @@ ynh_add_app_dependencies () {
 	replace=${replace:-0}
 
 	local current_dependencies=""
-	if [ $replace -eq 0 ]
+	if [ "$replace" -eq 0 ]
 	then
 		local dep_app=${app//_/-}	# Replace all '_' by '-'
 		if ynh_package_is_installed --package="${dep_app}-ynh-deps"
 		then
-			current_dependencies="$(dpkg-query --show --showformat='${Depends}' ${dep_app}-ynh-deps) "
+			current_dependencies="$(dpkg-query --show --showformat='${Depends}' "${dep_app}"-ynh-deps) "
 		fi
 
 		current_dependencies=${current_dependencies// | /|}