diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/viewsupport/CElementImageProvider.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/viewsupport/CElementImageProvider.java
index 02058c17568..56c78494175 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/viewsupport/CElementImageProvider.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/viewsupport/CElementImageProvider.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2005, 2015 IBM Corporation and others.
+ * Copyright (c) 2005, 2023 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -13,6 +13,7 @@
  *     QNX Software System
  *     Markus Schorn (Wind River Systems)
  *     Anton Leherbauer (Wind River Systems)
+ *     John Dallaway - use external file adornment (#563)
  *******************************************************************************/
 package org.eclipse.cdt.internal.ui.viewsupport;
 
@@ -596,6 +597,9 @@ public class CElementImageProvider {
 								flags |= CElementImageDescriptor.WARNING;
 							}
 						}
+						if ((element instanceof ITranslationUnit) && (null == element.getResource())) {
+							flags |= CElementImageDescriptor.EXTERNAL_FILE;
+						}
 					}
 				}
 			} catch (CModelException e) {