diff --git a/gui.py b/gui.py
index f2fc95d..283e0d2 100644
--- a/gui.py
+++ b/gui.py
@@ -695,7 +695,7 @@ if __name__ == "__main__":
             if len(values["index_path"].strip()) == 0:
                 sg.popup(i18n("Please choose the .index file"))
                 return False
-            pattern = re.compile("[^\x00-\x7F]+")
+            pattern = re.compile("[^\x00-\x7f]+")
             if pattern.findall(values["pth_path"]):
                 sg.popup(i18n("pth path cannot contain unicode characters"))
                 return False