diff --git a/Images/Sources/Images/Favicons/FaviconDownloader.swift b/Images/Sources/Images/Favicons/FaviconDownloader.swift
index 542f88de3..dbc467342 100644
--- a/Images/Sources/Images/Favicons/FaviconDownloader.swift
+++ b/Images/Sources/Images/Favicons/FaviconDownloader.swift
@@ -163,6 +163,8 @@ public protocol FaviconDownloaderDelegate {
 
 	@objc func didLoadFavicon(_ note: Notification) {
 
+		assert(Thread.isMainThread)
+		
 		guard let singleFaviconDownloader = note.object as? SingleFaviconDownloader else {
 			return
 		}