diff --git a/event.go b/event.go
index ad55ecf..fd3fbd2 100644
--- a/event.go
+++ b/event.go
@@ -339,11 +339,13 @@ func (window *window) handleMotionNotify (
 	}
 
 	underneath := window.boxUnder(image.Pt(x, y), eventCategoryMouse)
-	window.hover(underneath)
-	
-	if !handled {
-		underneath.handleMouseMove()
+	if underneath != nil {
+		window.hover(underneath)
+		if !handled {
+			underneath.handleMouseMove()
+		}
 	}
+	
 }
 
 func (window *window) compressExpose (