diff --git a/repo2docker/buildpacks/conda/activate-conda.sh b/repo2docker/buildpacks/conda/activate-conda.sh
index 14c46db8..15b771e7 100755
--- a/repo2docker/buildpacks/conda/activate-conda.sh
+++ b/repo2docker/buildpacks/conda/activate-conda.sh
@@ -7,8 +7,8 @@ done
 if [[ "${KERNEL_PYTHON_PREFIX}" != "${NB_PYTHON_PREFIX}" ]]; then
     # if the kernel is a separate env, stack them
     # so both are on PATH, notebook first
-    mamba activate ${KERNEL_PYTHON_PREFIX}
-    mamba activate --stack ${NB_PYTHON_PREFIX}
+    micromamba activate ${KERNEL_PYTHON_PREFIX}
+    micromamba activate --stack ${NB_PYTHON_PREFIX}
 
     # even though it's second on $PATH
     # make sure CONDA_DEFAULT_ENV is the *kernel* env
@@ -17,5 +17,5 @@ if [[ "${KERNEL_PYTHON_PREFIX}" != "${NB_PYTHON_PREFIX}" ]]; then
     # which only contains UI when the two are different
     export CONDA_DEFAULT_ENV="${KERNEL_PYTHON_PREFIX}"
 else
-    mamba activate ${NB_PYTHON_PREFIX}
+    micromamba activate ${NB_PYTHON_PREFIX}
 fi