diff --git a/resources/assets/javascripts/lib/files.js b/resources/assets/javascripts/lib/files.js
index 2e79bbe324b189a1215f9cfbf112785bbd4e9fbd..9d06a18ea153237905a759283e3095d4a58e750a 100644
--- a/resources/assets/javascripts/lib/files.js
+++ b/resources/assets/javascripts/lib/files.js
@@ -80,7 +80,7 @@ const Files = {
         if (file.size > Files.uploadConstraints.file_size) {
             return false;
         }
-        var ending = file.name.lastIndexOf('.') !== -1 ? file.name.substr(file.name.lastIndexOf('.') + 1) : '';
+        var ending = file.name.lastIndexOf('.') !== -1 ? file.name.substr(file.name.lastIndexOf('.') + 1).toLowerCase() : '';
 
         if (Files.uploadConstraints.type === 'allow') {
             return $.inArray(ending, Files.uploadConstraints.file_types) === -1;