diff --git a/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/DesignerEditor.java b/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/DesignerEditor.java
index 297af0b56..651bcd2ea 100644
--- a/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/DesignerEditor.java
+++ b/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/DesignerEditor.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2011, 2024 Google, Inc.
+ * Copyright (c) 2011, 2026 Google, Inc. and others.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License 2.0 which is available at
@@ -138,7 +138,11 @@ private boolean canDesignInput() {
 	void activated() {
 		if (m_firstActivation) {
 			m_firstActivation = false;
-			m_multiMode.editorActivatedFirstTime();
+			getRootControl().getDisplay().asyncExec(() -> {
+				if (!m_multiMode.isDisposed()) {
+					m_multiMode.editorActivatedFirstTime();
+				}
+			});
 		}
 	}
 
diff --git a/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/MultiMode.java b/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/MultiMode.java
index 5c5c09215..13add79c7 100644
--- a/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/MultiMode.java
+++ b/org.eclipse.wb.core.java/src/org/eclipse/wb/internal/core/editor/multi/MultiMode.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2011 Google, Inc.
+ * Copyright (c) 2011, 2026 Google, Inc. and others.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License 2.0 which is available at
@@ -35,6 +35,7 @@ public abstract class MultiMode implements IMultiMode {
 	protected final SourcePage m_sourcePage;
 	protected final DesignPage m_designPage;
 	protected final List<IEditorPage> m_additionalPages = new ArrayList<>();
+	private boolean m_disposed;
 
 	////////////////////////////////////////////////////////////////////////////
 	//
@@ -136,6 +137,7 @@ void create(Composite parent) {
 	 * Disposes this {@link MultiMode}.
 	 */
 	void dispose() {
+		m_disposed = true;
 		m_sourcePage.dispose();
 		m_designPage.dispose();
 		for (IEditorPage page : m_additionalPages) {
@@ -143,6 +145,10 @@ void dispose() {
 		}
 	}
 
+	boolean isDisposed() {
+		return m_disposed;
+	}
+
 	/**
 	 * Notifies that {@link DesignerEditor} has now new input, so new {@link ICompilationUnit} to
 	 * parse.