diff --git a/packages/ide/src/fill/dialog.ts b/packages/ide/src/fill/dialog.ts
index acee2bdca587..c8fd5a302471 100644
--- a/packages/ide/src/fill/dialog.ts
+++ b/packages/ide/src/fill/dialog.ts
@@ -130,6 +130,9 @@ export class Dialog {
 	 * Show the dialog.
 	 */
 	public show(): void {
+		if (document.querySelector(`.${this.overlay.className}`)) {
+			throw new Error ("Overlay is already open");
+		}
 		if (!this.cachedActiveElement) {
 			this.cachedActiveElement = document.activeElement as HTMLElement;
 			(document.querySelector(".monaco-workbench") || document.body).appendChild(this.overlay);