diff --git a/SilicaViewer/SilicaEngine.swift b/SilicaViewer/SilicaEngine.swift
index d9c8d69..82f2a9a 100644
--- a/SilicaViewer/SilicaEngine.swift
+++ b/SilicaViewer/SilicaEngine.swift
@@ -61,7 +61,9 @@ class SilicaEngine {
                     maskContext?.fill(document.cgRect())
                     
                     for chunk in layer.mask!.chunks {
-                        maskContext?.draw(chunk.image!, in: document.getChunkRect(chunk))
+                        if let image = chunk.image {
+                            maskContext?.draw(image, in: document.getChunkRect(chunk))
+                        }
                     }
                 }