diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 9058023527..8de672f6c5 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -106,40 +106,10 @@ From the root of the repository, you can then run the `make livedoc` command to
 
 All classes and function are automatically picked up and added to the documentation. The only thing you have to do is to add an entry to the relevant file in the [`docs/releases` directory](docs/releases).
 
-## Building Cython extensions
-
-```sh
-make build-cython
-```
-
-## Building Rust extensions
-
-Debug settings:
-
-```sh
-make develop
-```
-
-Release settings:
-
-```sh
-make build-rust
-```
-
-After building the project by modifying the rust part of the codebase (changing the project architecture, renaming it, etc.), it happens that by importing `river,` the python process is killed. If this happens, we invite you to remove the following things and start a new build:
-
-```sh
-# remove all .so output from rust ie river/stats/_rust_stats.cpython*
-rm -rf target
-rm -rf river.egg-info
-rm Cargo.lock
-rm -rf build
-```
-
 ## Build Cython and Rust extensions
 
 ```sh
-make build_all
+poetry install
 ```
 
 ## Testing
@@ -182,10 +152,11 @@ make execute-notebooks
 2. Run `make execute-notebooks` just to be safe
 3. Run the [benchmarks](benchmarks)
 4. Bump the version in `river/__version__.py`
-5. Tag and date the `docs/releases/unreleased.md` file
-6. Commit and push
-7. Wait for CI to [run the unit tests](https://github.com/online-ml/river/actions/workflows/ci.yml)
-8. Push the tag:
+5. Bump the version in `pyproject.toml`
+6. Tag and date the `docs/releases/unreleased.md` file
+7. Commit and push
+8. Wait for CI to [run the unit tests](https://github.com/online-ml/river/actions/workflows/ci.yml)
+9. Push the tag:
 
 ```sh
 RIVER_VERSION=$(python -c "import river; print(river.__version__)")
diff --git a/Makefile b/Makefile
index 748db226f2..b5eb969486 100644
--- a/Makefile
+++ b/Makefile
@@ -25,15 +25,3 @@ livedoc: doc
 
 rebase:
 	git fetch && git rebase origin/main
-
-develop:
-	python ./setup.py develop
-
-build-cython:
-	python setup.py build_ext --inplace --force
-
-build-rust:
-	python setup.py build_rust --inplace --release
-
-build:
-	python setup.py build_rust --inplace --release build_ext  --inplace --force
diff --git a/pyproject.toml b/pyproject.toml
index ebbfe1c8df..560377e64a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "river"
-version = "0.20.1"
+version = "0.21.0"
 description = "Online machine learning in Python"
 readme = "README.md"
 homepage = "https://riverml.xyz/"
diff --git a/river/drift/adwin_c.pyx b/river/drift/adwin_c.pyx
index bddebd63a1..322859c780 100644
--- a/river/drift/adwin_c.pyx
+++ b/river/drift/adwin_c.pyx
@@ -88,7 +88,7 @@ cdef class AdaptiveWindowing:
             If True then a change is detected.
 
         """
-        self._update(value)
+        return self._update(value)
 
     cdef bint _update(self, double value):
         # Increment window with one element