diff --git a/repo2docker/buildpacks/conda/install-base-env.bash b/repo2docker/buildpacks/conda/install-base-env.bash
index bfe2b828..4eb93f00 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=1.5.8
+export MAMBA_VERSION=1.5.9
 export CONDA_VERSION=24.5.0
 
 URL="https://anaconda.org/conda-forge/micromamba/${MAMBA_VERSION}/download/${CONDA_PLATFORM}/micromamba-${MAMBA_VERSION}-0.tar.bz2"
diff --git a/tests/conda/py35-binder-dir/verify b/tests/conda/py35-binder-dir/verify
index 42eb7e45..ef166558 100755
--- a/tests/conda/py35-binder-dir/verify
+++ b/tests/conda/py35-binder-dir/verify
@@ -16,12 +16,12 @@ v = out.split()[1]
 assert v[:3] == "3.5", out
 
 out = sh(["micromamba", "--version"])
-assert out == "1.5.8", out
+assert out == "1.5.9", out
 
 out = sh(["mamba", "--version"])
 assert (
     out
-    == """mamba 1.5.8
+    == """mamba 1.5.9
 conda 24.5.0"""
 ), out