diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index df64127..5e0f6c3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,7 @@ jobs:
     with:
       IMAGE_NAME: dwolla/jenkins-agent-python
       TAG_NAME: CORE_TAG
+      CORE_TAG: 3261.v9c670a_4748a_9-8-jdk11-2bbea7f
     secrets:
       DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
       DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
diff --git a/Dockerfile b/Dockerfile
index bf3ff5c..9f55ada 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -44,6 +44,9 @@ RUN chown -R jenkins:jenkins "${JENKINS_HOME}/.pyenv"
 
 USER jenkins
 
-RUN pyenv install 3.9
+RUN pyenv install 3.11
 
-RUN pyenv global 3.9
+RUN pyenv global 3.11
+
+# Prepend shims so `python3` / `pip` use pyenv (not Debian /usr/bin/python3).
+ENV PATH $PYENV_ROOT/shims:$PYENV_ROOT/bin:$PATH