diff --git a/src/client/graphics/layers/BuildMenu.ts b/src/client/graphics/layers/BuildMenu.ts
index 9a6fcc942..645c5a8d1 100644
--- a/src/client/graphics/layers/BuildMenu.ts
+++ b/src/client/graphics/layers/BuildMenu.ts
@@ -136,6 +136,11 @@ export class BuildMenu extends LitElement implements Layer {
       if (!this.game.myPlayer()?.isAlive()) {
         return;
       }
+      if (!this._hidden) {
+        // Players sometimes hold control while building a unit,
+        // so if the menu is already open, ignore the event.
+        return;
+      }
       const clickedCell = this.transformHandler.screenToWorldCoordinates(
         e.x,
         e.y,