diff --git a/src/Jackett.Common/Definitions/anilibria.yml b/src/Jackett.Common/Definitions/anilibria.yml
index e054ceb3e..7462eb62a 100644
--- a/src/Jackett.Common/Definitions/anilibria.yml
+++ b/src/Jackett.Common/Definitions/anilibria.yml
@@ -167,6 +167,7 @@ search:
           args: ["(?i)^(?!S\\d+).*", ""]
     _season_number_alternative:
       selector: ..names.alternative
+      optional: true
       filters:
         - name: re_replace
           args: ["(?i)\\bPart\\s*\\d+\\s*$", ""]