diff --git a/bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java b/bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java
index 2e0901417b56..54eebcb244b0 100644
--- a/bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java
+++ b/bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java
@@ -30,6 +30,7 @@
 import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.dialogs.MessageDialogWithToggle;
 import org.eclipse.jface.preference.IPreferenceStore;
+import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.jface.window.IShellProvider;
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.swt.widgets.Shell;
@@ -130,6 +131,25 @@ public CloseUnrelatedProjectsAction(IShellProvider provider){
 		initAction();
 	}
 
+	/**
+	 * Overrides to avoid calling the expensive
+	 * {@code computeRelated(List)} during selection changes. Uses only
+	 * the raw selection to determine enablement.
+	 */
+	@Override
+	protected boolean updateSelection(IStructuredSelection s) {
+		selectionDirty = true;
+		if (!selectionIsOfType(IResource.PROJECT)) {
+			return false;
+		}
+		for (IResource resource : super.getSelectedResources()) {
+			if (resource instanceof IProject project && project.isOpen()) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	@Override
 	public void run() {
 		if (promptForConfirmation()) {