diff --git a/bundles/org.eclipse.e4.ui.css.workbench/src/org/eclipse/e4/ui/css/model/workbench/internal/elements/WMElement.java b/bundles/org.eclipse.e4.ui.css.workbench/src/org/eclipse/e4/ui/css/model/workbench/internal/elements/WMElement.java
index a64e0c0..9b5739e 100644
--- a/bundles/org.eclipse.e4.ui.css.workbench/src/org/eclipse/e4/ui/css/model/workbench/internal/elements/WMElement.java
+++ b/bundles/org.eclipse.e4.ui.css.workbench/src/org/eclipse/e4/ui/css/model/workbench/internal/elements/WMElement.java
@@ -65,7 +65,11 @@
 	 * @return CSS ID
 	 */
 	public static String getID(MApplicationElement element) {
-		return element.getElementId().replace(".", "-");
+		String elementId = element.getElementId();
+		if (elementId == null) {
+			return null;
+		}
+		return elementId.replace(".", "-");
 	}
 
 	protected String localName;