diff --git a/src/lib/elements/element_input_files_tbl.svelte b/src/lib/elements/element_input_files_tbl.svelte
index 22e9d5e6..a1b977f2 100644
--- a/src/lib/elements/element_input_files_tbl.svelte
+++ b/src/lib/elements/element_input_files_tbl.svelte
@@ -99,7 +99,7 @@ async function process_file_list(file_list: FileList) {
         // console.log(filename);
         file_data['filename'] = filename;
 
-        let guessed_extension = ae_util.guess_file_extension(filename);
+        let guessed_extension = ae_util.guess_file_extension(filename).toLowerCase();
         file_data['guessed_extension'] = guessed_extension;
 
         file_data['type'] = file_item.type;