diff --git a/bauh/gems/appimage/controller.py b/bauh/gems/appimage/controller.py
index 88ba7f98..8c648f93 100644
--- a/bauh/gems/appimage/controller.py
+++ b/bauh/gems/appimage/controller.py
@@ -528,13 +528,13 @@ class AppImageManager(SoftwareManager, SettingsController):
         finally:
             releases_con.close()
 
-    def _find_desktop_file(self, folder: str) -> str:
+    def _find_desktop_file(self, folder: str) -> Optional[str]:
         for r, d, files in os.walk(folder):
             for f in files:
                 if f.endswith('.desktop'):
                     return f
 
-    def _find_icon_file(self, folder: str) -> str:
+    def _find_icon_file(self, folder: str) -> Optional[str]:
         for f in glob.glob(folder + ('/**' if not folder.endswith('/') else '**'), recursive=True):
             if RE_ICON_ENDS_WITH.match(f):
                 return f
diff --git a/bauh/gems/appimage/util.py b/bauh/gems/appimage/util.py
index d39fd662..43edda03 100644
--- a/bauh/gems/appimage/util.py
+++ b/bauh/gems/appimage/util.py
@@ -1,15 +1,16 @@
 import os
 import re
+from typing import Optional
 
 RE_DESKTOP_EXEC = re.compile(r'(Exec\s*=(.+)(\n?))')
 RE_MANY_SPACES = re.compile(r'\s+')
 
 
-def find_appimage_file(folder: str) -> str:
+def find_appimage_file(folder: str) -> Optional[str]:
     for r, d, files in os.walk(folder):
         for f in files:
             if f.lower().endswith('.appimage'):
-                return '{}/{}'.format(folder, f)
+                return f'{folder}/{f}'
 
 
 def replace_desktop_entry_exec_command(desktop_entry: str, appname: str, file_path: str) -> str:
@@ -30,12 +31,12 @@ def replace_desktop_entry_exec_command(desktop_entry: str, appname: str, file_pa
 
             for idx in range(len(words)):
                 if words[idx].lower() == treated_name:
-                    words[idx] = '"{}"'.format(file_path)
+                    words[idx] = f'"{file_path}"'
                     changed = True
                     break
 
             if not changed:
-                words = ['"{}"'.format(file_path)]
+                words = [f'"{file_path}"']
 
             final_entry = final_entry.replace(full_match, full_match.replace(exec_groups[1], ' '.join(words)))