diff --git a/js/ui/tool/stamp.js b/js/ui/tool/stamp.js
index 3ef8476..4bf2fa3 100644
--- a/js/ui/tool/stamp.js
+++ b/js/ui/tool/stamp.js
@@ -153,7 +153,7 @@ const stampTool = () =>
 				};
 
 				state.movecb = (evn) => {
-					if (evn.target.id === "overlayCanvas") {
+					if (evn.target && evn.target.id === "overlayCanvas") {
 						let x = evn.x;
 						let y = evn.y;
 						if (state.snapToGrid) {