diff --git a/module/utils/fs.mjs b/module/utils/fs.mjs
index f0b02fd..1edb4cd 100644
--- a/module/utils/fs.mjs
+++ b/module/utils/fs.mjs
@@ -147,6 +147,7 @@ export async function uploadFile(path, file) {
 };
 
 export function determineFileExtension(file) {
+	if (!file) return null;
 	for (const [short, long] of Object.entries(CONST.IMAGE_FILE_EXTENSIONS)) {
 		if (long === file.type) {
 			return short;