diff --git a/core/src/main/java/org/kiwix/kiwixmobile/core/downloader/DownloaderImpl.kt b/core/src/main/java/org/kiwix/kiwixmobile/core/downloader/DownloaderImpl.kt
index 4ba9387a6..908b91817 100644
--- a/core/src/main/java/org/kiwix/kiwixmobile/core/downloader/DownloaderImpl.kt
+++ b/core/src/main/java/org/kiwix/kiwixmobile/core/downloader/DownloaderImpl.kt
@@ -43,7 +43,7 @@ class DownloaderImpl @Inject constructor(
   }
 
   private fun urlProvider(book: Book): Observable<String> =
-    if (book.url?.endsWith("meta4") == true) kiwixService.getMetaLinks(book.url)
+    if (book.url?.endsWith("meta4") == true) kiwixService.getMetaLinks(book.url!!)
       .map { it.relevantUrl.value }
     else Observable.just(book.url)