diff --git a/org.eclipse.xtext.ui.tests/src-longrunning/org/eclipse/xtext/ui/tests/editor/DirtyStateEditorSupportIntegrationTest.java b/org.eclipse.xtext.ui.tests/src-longrunning/org/eclipse/xtext/ui/tests/editor/DirtyStateEditorSupportIntegrationTest.java
index c6984cb1f1c..93058528b99 100644
--- a/org.eclipse.xtext.ui.tests/src-longrunning/org/eclipse/xtext/ui/tests/editor/DirtyStateEditorSupportIntegrationTest.java
+++ b/org.eclipse.xtext.ui.tests/src-longrunning/org/eclipse/xtext/ui/tests/editor/DirtyStateEditorSupportIntegrationTest.java
@@ -144,7 +144,7 @@ public void testUndoRedo() throws Exception {
 		try (FileWriter fw = new FileWriter(externalEditFile)) {
 			fw.write("");
 		}
-		
+		sleep(250);
 		assertFalse(fileDocumentProvider.isSynchronized(editor.getEditorInput()));
 
 		editor.setFocus();