diff --git a/repo2docker/buildpacks/conda/activate-conda.sh b/repo2docker/buildpacks/conda/activate-conda.sh
index b5a54e30..d3732c8f 100755
--- a/repo2docker/buildpacks/conda/activate-conda.sh
+++ b/repo2docker/buildpacks/conda/activate-conda.sh
@@ -1,11 +1,24 @@
-# enable conda and activate the notebook environment
-set -e
+set -ex
+
+# Setup conda
+CONDA_PROFILE="${CONDA_DIR}/etc/profile.d/conda.sh"
+echo "Activating profile: ${CONDA_PROFILE}"
+test -f $CONDA_PROFILE && . $CONDA_PROFILE
+
+# Setup micromamba
 eval $(micromamba shell hook -s posix -r ${CONDA_DIR})
-for name in conda mamba; do
-    CONDA_PROFILE="${CONDA_DIR}/etc/profile.d/${name}.sh"
-    echo "Activating profile: ${CONDA_PROFILE}"
-    test -f $CONDA_PROFILE && . $CONDA_PROFILE
-done
+
+# Setup mamba
+export MAMBA_ROOT_PREFIX="${CONDA_DIR}"
+__mamba_setup="$("${CONDA_DIR}/bin/mamba" shell hook --shell posix 2> /dev/null)"
+if [ $? -eq 0 ]; then
+    eval "$__mamba_setup"
+else
+    alias mamba="${CONDA_DIR}/bin/mamba"  # Fallback on help from mamba activate
+fi
+unset __mamba_setup
+
+# Activate the environment
 if [[ "${KERNEL_PYTHON_PREFIX}" != "${NB_PYTHON_PREFIX}" ]]; then
     # if the kernel is a separate env, stack them
     # so both are on PATH, notebook first
@@ -22,4 +35,4 @@ else
     mamba activate ${NB_PYTHON_PREFIX}
 fi
 
-set +e
+set +ex
diff --git a/repo2docker/buildpacks/conda/install-base-env.bash b/repo2docker/buildpacks/conda/install-base-env.bash
index a26eff59..a96faf59 100755
--- a/repo2docker/buildpacks/conda/install-base-env.bash
+++ b/repo2docker/buildpacks/conda/install-base-env.bash
@@ -5,7 +5,7 @@ set -ex
 
 cd $(dirname $0)
 
-export MAMBA_VERSION="2.0.5"
+export MAMBA_VERSION="2.0.7.rc1"
 export CONDA_VERSION=24.11.0
 
 URL="https://anaconda.org/conda-forge/micromamba/${MAMBA_VERSION}/download/${CONDA_PLATFORM}/micromamba-${MAMBA_VERSION}-0.tar.bz2"
@@ -36,7 +36,10 @@ update_dependencies: false
 # channel_priority: flexible
 EOT
 
-micromamba install conda=${CONDA_VERSION} mamba=${MAMBA_VERSION} -y
+micromamba install \
+    -c conda-forge/label/mamba_prerelease \
+    -c conda-forge \
+    conda=${CONDA_VERSION} mamba=${MAMBA_VERSION} -y
 
 echo "installing notebook env:"
 cat "${NB_ENVIRONMENT_FILE}"
diff --git a/tests/conda/py35-binder-dir/verify b/tests/conda/py35-binder-dir/verify
index 5b01d9a9..bb43f7f6 100755
--- a/tests/conda/py35-binder-dir/verify
+++ b/tests/conda/py35-binder-dir/verify
@@ -16,10 +16,10 @@ v = out.split()[1]
 assert v[:3] == "3.5", out
 
 out = sh(["micromamba", "--version"])
-assert out == "2.0.5", out
+assert out == "2.0.7.rc1", out
 
 out = sh(["mamba", "--version"])
-assert out == "2.0.5", out
+assert out == "2.0.7.rc1", out
 
 
 sh([kernel_python, "-c", "import numpy"])