diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ec87c3b2e3c22330c02c72c6b758bc9b06aff424..7f7ac7d4d5f2e9e4b38549bf8cc1d03ee09b6a9d 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -91,7 +91,6 @@ build-book:
       - "**/_sources/**"
       - "**/__pycache__/**"
       - "**/*.pyc"
-      - "**/_ext/**"
       - "**/*.pickle"
       - book/_build/.doctrees/**
       - book/_build/jupyter_cache/**