diff --git a/tests/plugins/uploadwidget/manual/_helpers/xhrerror.js b/tests/plugins/uploadwidget/manual/_helpers/xhrerror.js
index 5433c161779..2f4fadeb552 100644
--- a/tests/plugins/uploadwidget/manual/_helpers/xhrerror.js
+++ b/tests/plugins/uploadwidget/manual/_helpers/xhrerror.js
@@ -7,14 +7,31 @@
 
 // Mock the real XMLHttpRequest so the upload test may show the effect of an error during upload.
 
+window.FormData = function() {
+	var total, filename;
+	return {
+		append: function( name, file, filename ) {
+			total = file.size;
+			filename = filename;
+		},
+		getTotal: function() {
+			return total;
+		},
+		getFileName: function() {
+			return filename;
+		}
+	};
+};
+
 window.XMLHttpRequest = function() {
 	return {
 		open: function() {},
 
-		send: function() {
+		send: function( formData ) {
 			// Total file size.
-			var loaded = 0,
-				step = 10,
+			var total = formData.getTotal(),
+				loaded = 0,
+				step = Math.round( total / 10 ),
 				onprogress = this.onprogress,
 				onerror = this.onerror,
 				interval;
diff --git a/tests/plugins/uploadwidget/manual/error.md b/tests/plugins/uploadwidget/manual/error.md
index 06756ffe422..60b1e87b4a8 100644
--- a/tests/plugins/uploadwidget/manual/error.md
+++ b/tests/plugins/uploadwidget/manual/error.md
@@ -7,5 +7,5 @@ This test emulates an error during upload. When upload hits 50% an error occurs.
 
  * Drop an image.
  * Check if `upload widget` is displayed.
- * Check if image is removed after it reaches 50% of progress and no artifacts left.
+ * Check if image is removed when it reaches 50% of progress and no artifacts left.
  * Check if you see a message about the error.
\ No newline at end of file