diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 89a283d0..62557f06 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -20,7 +20,7 @@ SimpleLogin backend consists of 2 main components:
 ## Install dependencies
 
 The project requires:
-- Python 3.10 and [rye](https://github.com/astral-sh/rye) to manage dependencies
+- Python 3.10 and poetry to manage dependencies
 - Node v10 for front-end.
 - Postgres 13+
 
@@ -28,7 +28,7 @@ First, install all dependencies by running the following command.
 Feel free to use `virtualenv` or similar tools to isolate development environment.
 
 ```bash
-rye sync
+poetry sync
 ```
 
 On Mac, sometimes you might need to install some other packages via `brew`:
@@ -55,7 +55,7 @@ brew install -s re2 pybind11
 We use pre-commit to run all our linting and static analysis checks. Please run
 
 ```bash
-rye run pre-commit install
+poetry run pre-commit install
 ```
 
 To install it in your development environment.
@@ -160,25 +160,25 @@ Here are the small sum-ups of the directory structures and their roles:
 The code is formatted using [ruff](https://github.com/astral-sh/ruff), to format the code, simply run
 
 ```
-rye run ruff format .
+poetry run ruff format .
 ```
 
 The code is also checked with `flake8`, make sure to run `flake8` before creating the pull request by
 
 ```bash
-rye run flake8
+poetry run flake8
 ```
 
 For HTML templates, we use `djlint`. Before creating a pull request, please run
 
 ```bash
-rye run djlint --check templates
+poetry run djlint --check templates
 ```
 
 If some files aren't properly formatted, you can format all files with
 
 ```bash
-rye run djlint --reformat .
+poetry run djlint --reformat .
 ```
 
 ## Test sending email
@@ -226,3 +226,26 @@ Some features require a job handler (such as GDPR data export). To test such fea
 ```bash
 python job_runner.py
 ```
+
+# Setup for Mac
+
+There are several ways to setup Python and manage the project dependencies on Mac. For info we have successfully used this setup on a Mac silicon:
+
+```bash
+# we haven't managed to make python 3.12 work
+brew install python3.10
+
+# make sure to update the PATH so python, pip point to Python3
+# for us it can be done by adding "export PATH=/opt/homebrew/opt/python@3.10/libexec/bin:$PATH" to .zprofile
+
+# Although pipx is the recommended way to install poetry,
+# install pipx via brew will automatically install python 3.12
+# and poetry will then use python 3.12
+# so we recommend using poetry this way instead
+curl -sSL https://install.python-poetry.org | python3 -
+
+poetry install
+
+# activate the virtualenv and you should be good to go!
+source .venv/bin/activate
+```
\ No newline at end of file
diff --git a/app/user_settings.py b/app/user_settings.py
index cef224dd..136a18b3 100644
--- a/app/user_settings.py
+++ b/app/user_settings.py
@@ -16,12 +16,13 @@ class CannotSetMailbox(Exception):
 
 
 def set_default_alias_domain(user: User, domain_name: Optional[str]):
-    if domain_name is None:
+    if not domain_name:
         LOG.i(f"User {user} has set no domain as default domain")
         user.default_alias_public_domain_id = None
         user.default_alias_custom_domain_id = None
         Session.flush()
         return
+
     sl_domain: SLDomain = SLDomain.get_by(domain=domain_name)
     if sl_domain:
         if sl_domain.hidden: