diff --git a/python/sdist/amici/_installation/__init__.py b/python/sdist/amici/_installation/__init__.py
new file mode 100644
index 0000000000..0b3315553e
--- /dev/null
+++ b/python/sdist/amici/_installation/__init__.py
@@ -0,0 +1 @@
+"""Private installation helper functions for AMICI."""
diff --git a/python/sdist/amici/custom_commands.py b/python/sdist/amici/_installation/custom_commands.py
similarity index 99%
rename from python/sdist/amici/custom_commands.py
rename to python/sdist/amici/_installation/custom_commands.py
index fabe39b48e..0616d75db2 100644
--- a/python/sdist/amici/custom_commands.py
+++ b/python/sdist/amici/_installation/custom_commands.py
@@ -12,7 +12,7 @@
 from setuptools.command.install_lib import install_lib
 from setuptools.command.sdist import sdist
 
-from amici.swig import fix_typehints
+from amici._installation.swig import fix_typehints
 
 
 class AmiciInstall(install):
diff --git a/python/sdist/amici/swig.py b/python/sdist/amici/_installation/swig.py
similarity index 100%
rename from python/sdist/amici/swig.py
rename to python/sdist/amici/_installation/swig.py
diff --git a/python/sdist/amici/exporters/sundials/templates/setup.template.py b/python/sdist/amici/exporters/sundials/templates/setup.template.py
index 2439704e66..6bff45aeb8 100644
--- a/python/sdist/amici/exporters/sundials/templates/setup.template.py
+++ b/python/sdist/amici/exporters/sundials/templates/setup.template.py
@@ -6,7 +6,7 @@
 from pathlib import Path
 
 from amici import _get_amici_path
-from amici.custom_commands import AmiciBuildCMakeExtension
+from amici._installation.custom_commands import AmiciBuildCMakeExtension
 from cmake_build_extension import CMakeExtension
 from setuptools import find_namespace_packages, setup
 
diff --git a/python/sdist/setup.py b/python/sdist/setup.py
index bd32908ca1..ab5177d2ef 100755
--- a/python/sdist/setup.py
+++ b/python/sdist/setup.py
@@ -22,7 +22,7 @@
 # package already for installation
 sys.path.insert(0, os.path.dirname(__file__))
 
-from amici.custom_commands import (
+from amici._installation.custom_commands import (
     AmiciBuildCMakeExtension,
     AmiciBuildPy,
     AmiciDevelop,