diff --git a/adafruit_slideshow.py b/adafruit_slideshow.py
index 3072bcd..feff825 100755
--- a/adafruit_slideshow.py
+++ b/adafruit_slideshow.py
@@ -244,11 +244,11 @@ def _check_json_file(file):
         # Load the image names before setting order so they can be reordered.
         self._img_start = None
         self._file_list = [
-            folder + f
+            folder + "/" + f
             for f in os.listdir(folder)
             if (
                 not f.startswith(".")
-                and (f.endswith(".bmp") or _check_json_file(folder + f))
+                and (f.endswith(".bmp") or _check_json_file(folder + "/" + f))
             )
         ]