diff --git a/src/yunohost/utils/config.py b/src/yunohost/utils/config.py
index 0f18fad0d..e0fe1416b 100644
--- a/src/yunohost/utils/config.py
+++ b/src/yunohost/utils/config.py
@@ -1164,9 +1164,11 @@ class FileQuestion(Question):
         FileQuestion.upload_dirs += [upload_dir]
 
         logger.debug(f"Saving file {self.name} for file question into {file_path}")
-        if Moulinette.interface.type != "api" or (
-            self.value.startswith("/") and os.path.exists(self.value)
-        ):
+
+        def is_file_path(s):
+            return isinstance(s, str) and s.startswith("/") and os.path.exists(s)
+
+        if Moulinette.interface.type != "api" or is_file_path(self.value):
             content = read_file(str(self.value), file_mode="rb")
         else:
             content = b64decode(self.value)