diff --git a/manifest.toml b/manifest.toml
index 187a258..ab58fdd 100644
--- a/manifest.toml
+++ b/manifest.toml
@@ -23,9 +23,9 @@ architectures = "all"
 multi_instance = true
 ldap = "not_relevant"
 sso = "not_relevant"
-disk = "50M" # FIXME: replace with an **estimate** minimum disk requirement. e.g. 20M, 400M, 1G, ...
-ram.build = "50M" # FIXME: replace with an **estimate** minimum ram requirement. e.g. 50M, 400M, 1G, ...
-ram.runtime = "50M" # FIXME: replace with an **estimate** minimum ram requirement. e.g. 50M, 400M, 1G, ...
+disk = "50M"
+ram.build = "100M"
+ram.runtime = "50M"
 
 [install]
     [install.domain]
diff --git a/scripts/upgrade b/scripts/upgrade
index e3fcfa0..82e884c 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -17,19 +17,19 @@ source /usr/share/yunohost/helpers
 ynh_script_progression --message="Ensuring downward compatibility..." --weight=3
 
 # If fpm_footprint doesn't exist, create it
-if [ -z "$fpm_footprint" ]; then
+if [ -z "${fpm_footprint:-}" ]; then
     fpm_footprint=low
     ynh_app_setting_set --app="$app" --key=fpm_footprint --value="$fpm_footprint"
 fi
 
 # If fpm_free_footprint doesn't exist, create it
-if [ -z "$fpm_free_footprint" ]; then
+if [ -z "${fpm_free_footprint:-}" ]; then
     fpm_free_footprint=0
     ynh_app_setting_set --app="$app" --key=fpm_free_footprint --value="$fpm_free_footprint"
 fi
 
 # If fpm_usage doesn't exist, create it
-if [ -z "$fpm_usage" ]; then
+if [ -z "${fpm_usage:-}" ]; then
     fpm_usage=low
     ynh_app_setting_set --app="$app" --key=fpm_usage --value="$fpm_usage"
 fi