diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 555a229ae..885cf9d8f 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -120,6 +120,7 @@ Ben Kerman <ben@kermanic.org>
 Euan Kemp <euank@euank.com>
 Kieran Black <kieranlblack@gmail.com>
 XeR <github.com/XeR>
+Austin Siew <github.com/Aquafina-water-bottle>
 
 ********************
 
diff --git a/ts/reviewer/image_occlusion.ts b/ts/reviewer/image_occlusion.ts
index b0a83034b..319e27221 100644
--- a/ts/reviewer/image_occlusion.ts
+++ b/ts/reviewer/image_occlusion.ts
@@ -12,7 +12,11 @@ export function setupImageCloze(): void {
 }
 
 function setupImageClozeInner(): void {
-    const canvas: HTMLCanvasElement = document.querySelector("canvas")! as HTMLCanvasElement;
+    const canvas = document.querySelector("canvas") as HTMLCanvasElement | null;
+    if (canvas == null) {
+        return;
+    }
+
     canvas.style.maxWidth = "100%";
     canvas.style.maxHeight = "95vh";