diff --git a/scripts/sync-ebooks b/scripts/sync-ebooks
index 6d45aa59..98f3b895 100755
--- a/scripts/sync-ebooks
+++ b/scripts/sync-ebooks
@@ -92,7 +92,7 @@ while [ $# -gt 0 ]; do
 			shift 2
 			;;
 		--token)
-			check_arg '*[!0-9a-zA-Z]*' "$2" "Token is empty or contains illegal characters."
+			check_arg '*[!0-9a-zA-Z_]*' "$2" "Token is empty or contains illegal characters."
 			githubToken="$2"
 			shift 2
 			;;