diff --git a/CHANGELOG.md b/CHANGELOG.md
index 55c6d1bb..4b3ba5e8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ### Not yet released
 - Check that las/laz output can be read by pdal when running prediction.
+- Clean mamba build to reduce Docker image size (14.6GB to 9.2GB)
 
 ### 3.9.1
 - Remove usage of self-hosted runner and adapt tests accordingly:
diff --git a/Dockerfile b/Dockerfile
index 0b4c6fd3..6ba2f537 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,7 +10,10 @@ COPY environment.yml environment.yml
 # installation similar to https://github.com/mamba-org/micromamba-docker/issues/356)
 USER root
 
-RUN micromamba env create -f /app/environment.yml
+RUN micromamba env create -f /app/environment.yml \
+        && micromamba clean -a -y \
+        && rm -rf /root/.cache /opt/conda/pkgs \
+        && find /opt/conda -name '__pycache__' -type d -prune -exec rm -rf {} +
 
 ENV PATH=$PATH:/opt/conda/envs/myria3d/bin/
 # Need to export this for torch_geometric to find where cuda is.
diff --git a/myria3d/_version.py b/myria3d/_version.py
index ba0131c5..149e171f 100644
--- a/myria3d/_version.py
+++ b/myria3d/_version.py
@@ -1,4 +1,4 @@
-__version__ = "3.9.1"
+__version__ = "3.9.1.test"
 
 
 if __name__ == "__main__":