diff --git a/src/window.cpp b/src/window.cpp
index 83a95d6..311aad6 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -725,7 +725,8 @@ void Window::setContents(Bitmap *value)
 {
 	GUARD_DISPOSED;
 
-	value->ensureNonMega();
+	if (value)
+		value->ensureNonMega();
 
 	p->contents = value;
 	p->controlsVertDirty = true;