diff --git a/WebsiteGenerator/Files/ValidationLog.swift b/WebsiteGenerator/Files/ValidationLog.swift
index f2abf3e..2f81790 100644
--- a/WebsiteGenerator/Files/ValidationLog.swift
+++ b/WebsiteGenerator/Files/ValidationLog.swift
@@ -106,8 +106,12 @@ final class ValidationLog {
 
     func linkPreviewThumbnail(customFile: String?, for language: String, in folder: URL, source: String) -> String? {
         if let customFile = customFile {
-            #warning("Allow absolute urls for link preview thumbnails")
-            let customFileUrl = folder.appendingPathComponent(customFile)
+            let customFileUrl: URL
+            if customFile.starts(with: "/") {
+                customFileUrl = URL(fileURLWithPath: customFile)
+            } else {
+                customFileUrl = folder.appendingPathComponent(customFile)
+            }
             guard customFileUrl.exists else {
                 missing(customFile, requiredBy: "property 'linkPreviewImage' in metadata of \(source)")
                 return nil