diff --git a/gui/src/components/input/MaskCanvas.tsx b/gui/src/components/input/MaskCanvas.tsx
index d46f5cbc..3f1a0d87 100644
--- a/gui/src/components/input/MaskCanvas.tsx
+++ b/gui/src/components/input/MaskCanvas.tsx
@@ -156,6 +156,7 @@ export function MaskCanvas(props: MaskCanvasProps) {
   }, [source]);
 
   const styles: React.CSSProperties = {
+    border: '1px solid black',
     maxHeight: params.height.default,
     maxWidth: params.width.default,
   };