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 7aff6f28075..6d87ae4b2c0 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
@@ -8,28 +8,35 @@
  */
 package org.eclipse.xtext.ui.tests.editor;
 
+import java.io.File;
+import java.io.FileWriter;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 
 import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.emf.common.util.URI;
 import org.eclipse.jface.text.IUndoManager;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.custom.StyledText;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Event;
+import org.eclipse.ui.IFileEditorInput;
 import org.eclipse.xtext.resource.IEObjectDescription;
 import org.eclipse.xtext.resource.IResourceDescription;
 import org.eclipse.xtext.resource.IResourceServiceProvider;
 import org.eclipse.xtext.ui.editor.XtextEditor;
 import org.eclipse.xtext.ui.editor.XtextSourceViewer;
+import org.eclipse.xtext.ui.editor.model.IXtextDocument;
 import org.eclipse.xtext.ui.refactoring.ui.SyncUtil;
 import org.eclipse.xtext.ui.testing.AbstractEditorTest;
 import org.eclipse.xtext.ui.testing.util.IResourcesSetupUtil;
 import org.junit.Assert;
 import org.junit.Before;
+import org.junit.Ignore;
 import org.junit.Test;
 
 import com.google.common.collect.Iterables;
@@ -116,7 +123,62 @@ public void testUndoRedo() throws Exception {
 				.getQualifiedName().getLastSegment());
 		Iterables.getLast(events);
 	}
+	
+	/*
+	 * @see https://github.com/eclipse/xtext/issues/2385
+	 */
+	@Test public void testModifyFileInExternEditor() throws Exception {
+		IXtextDocument document = editor.getDocument();
+
+		Display.getDefault().readAndDispatch();
+		
+		assertNotEquals(document.get(), "");
+		
+		getWorkbench().getActiveWorkbenchWindow().getActivePage().getViewReferences()[0].getView(false).setFocus();
+		
+		File externalEditFile = ((IFileEditorInput)editor.getEditorInput()).getFile().getLocation().toFile();
+		try (FileWriter fw = new FileWriter(externalEditFile)) {
+			fw.write("");
+		}
+		editor.setFocus();
+		Job.getJobManager().join(ResourcesPlugin.FAMILY_AUTO_REFRESH, null);
+		syncUtil.yieldToQueuedDisplayJobs(new NullProgressMonitor());
+		syncUtil.waitForReconciler(editor);
+		assertEquals(document.get(), "");
+	}
+
+	/**
+	 * This test needs a manual button click.
+	 */
+	@Ignore
+	@Test public void testModifyDirtyFileInExternEditor() throws Exception {
+		IXtextDocument document = editor.getDocument();
 
+		Display.getDefault().readAndDispatch();
+		
+		assertNotEquals(document.get(), "");
+		document.set("/* Hello World! */");
+		assertEquals("/* Hello World! */", document.get());
+		assertTrue(editor.isDirty());
+		
+		getWorkbench().getActiveWorkbenchWindow().getActivePage().getViewReferences()[0].getView(false).setFocus();
+		
+		File externalEditFile = ((IFileEditorInput)editor.getEditorInput()).getFile().getLocation().toFile();
+		try (FileWriter fw = new FileWriter(externalEditFile)) {
+			fw.write("");
+		}
+		editor.setFocus();
+		// Dialog opens and the "Ignore file change" button has to be clicked.
+		Job.getJobManager().join(ResourcesPlugin.FAMILY_AUTO_REFRESH, null);
+		syncUtil.yieldToQueuedDisplayJobs(new NullProgressMonitor());
+		syncUtil.waitForReconciler(editor);
+		assertEquals(document.get(), "/* Hello World! */");
+		
+		assertTrue(editor.isDirty());
+		editor.doSave(new NullProgressMonitor());
+		assertFalse(editor.isDirty());
+	}
+	
 	private IEObjectDescription getFirstExportedObjectInLastEventDelta() {
 		return Iterables.getFirst(Iterables.getLast(events).getDeltas().get(0).getNew().getExportedObjects(), null);
 	}
diff --git a/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/XtextEditor.java b/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/XtextEditor.java
index 11159105a22..b62805f39a2 100755
--- a/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/XtextEditor.java
+++ b/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/XtextEditor.java
@@ -76,6 +76,7 @@
 import org.eclipse.ui.PlatformUI;
 import org.eclipse.ui.editors.text.TextEditor;
 import org.eclipse.ui.texteditor.DefaultMarkerAnnotationAccess;
+import org.eclipse.ui.texteditor.IDocumentProvider;
 import org.eclipse.ui.texteditor.ITextEditor;
 import org.eclipse.ui.texteditor.ITextEditorActionConstants;
 import org.eclipse.ui.texteditor.ITextEditorActionDefinitionIds;
@@ -327,6 +328,14 @@ public void doSave(IProgressMonitor progressMonitor) {
 		callback.afterSave(this);
 	}
 	
+	@Override
+	protected void performSave(boolean overwrite, IProgressMonitor progressMonitor) {
+		boolean unsyncOverwrite = !((XtextDocumentProvider)getDocumentProvider()).isSynchronized(getEditorInput());
+
+		super.performSave(overwrite || unsyncOverwrite, progressMonitor);
+	}
+	
+	
 	@Override
 	protected void updateState(final IEditorInput input) {
 		new DisplayRunnable() {
diff --git a/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/model/XtextDocumentProvider.java b/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/model/XtextDocumentProvider.java
index c8a804bf3ca..6e6dd1cbd55 100644
--- a/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/model/XtextDocumentProvider.java
+++ b/org.eclipse.xtext.ui/src/org/eclipse/xtext/ui/editor/model/XtextDocumentProvider.java
@@ -27,6 +27,7 @@
 import org.eclipse.core.filesystem.IFileInfo;
 import org.eclipse.core.filesystem.IFileStore;
 import org.eclipse.core.resources.IEncodedStorage;
+import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.IResourceStatus;
 import org.eclipse.core.resources.IStorage;
 import org.eclipse.core.runtime.Adapters;
@@ -410,6 +411,14 @@ public long getModificationStamp(Object element) {
 	
 	@Override
 	public boolean isSynchronized(Object element) {
+		if (!(element instanceof IFileEditorInput)) {
+			return super.isSynchronized(element);
+		}
+		IFileEditorInput input = (IFileEditorInput) element;
+		if (input.getFile() == null) {
+			return super.isSynchronized(element);
+		}
+		
 		ElementInfo info = getElementInfo(element);
 		long synchronizationStamp;
 		if (info instanceof FileInfo) {
@@ -419,7 +428,15 @@ public boolean isSynchronized(Object element) {
 		} else {
 			return super.isSynchronized(element);
 		}
-		return synchronizationStamp == getModificationStamp(element);
+
+		// Check has to fit the following method: 
+		// org.eclipse.ui.editors.text.FileDocumentProvider.checkSynchronizationState(long, IResource)
+		boolean isSynchronized = synchronizationStamp == getSynchronizationStamp(input.getFile());
+		if (!isSynchronized) {
+			// checks for is sync and triggers sync if necessary
+			input.getFile().isSynchronized(IResource.DEPTH_ZERO);
+		}
+		return isSynchronized;
 	}
 	
 	@Override