diff --git a/src/yunohost/app.py b/src/yunohost/app.py
index 0ce7a27c5..1d4a2ab30 100644
--- a/src/yunohost/app.py
+++ b/src/yunohost/app.py
@@ -55,6 +55,7 @@ from moulinette.utils.filesystem import (
 from yunohost.service import service_status, _run_service_command
 from yunohost.utils import packages
 from yunohost.utils.error import YunohostError, YunohostValidationError
+from yunohost.utils.filesystem import free_space_in_directory
 from yunohost.log import is_unit_operation, OperationLogger
 
 logger = getActionLogger("yunohost.app")
@@ -878,11 +879,10 @@ def app_install(
         manifest, extracted_app_folder = _extract_app_from_file(app)
     else:
         raise YunohostValidationError("app_unknown")
-    
+
     # Check if disk space available
-    size = os.statvfs('/')
     if free_space_in_directory("/") <= 512 * 1000 * 1000:
-	    raise YunohostValidationError("disk_space_not_sufficient_install")
+        raise YunohostValidationError("disk_space_not_sufficient_install")
 
     # Check ID
     if "id" not in manifest or "__" in manifest["id"]:
diff --git a/src/yunohost/backup.py b/src/yunohost/backup.py
index 99337b2f8..ecc5ae033 100644
--- a/src/yunohost/backup.py
+++ b/src/yunohost/backup.py
@@ -71,6 +71,7 @@ from yunohost.regenconf import regen_conf
 from yunohost.log import OperationLogger, is_unit_operation
 from yunohost.utils.error import YunohostError, YunohostValidationError
 from yunohost.utils.packages import ynh_packages_version
+from yunohost.utils.filesystem import free_space_in_directory
 from yunohost.settings import settings_get
 
 BACKUP_PATH = "/home/yunohost.backup"
@@ -2672,11 +2673,6 @@ def _recursive_umount(directory):
     return everything_went_fine
 
 
-def free_space_in_directory(dirpath):
-    stat = os.statvfs(dirpath)
-    return stat.f_frsize * stat.f_bavail
-
-
 def disk_usage(path):
     # We don't do this in python with os.stat because we don't want
     # to follow symlinks