diff --git a/docs/source/installation.rst b/docs/source/installation.rst
index d7fc639..c4b9e1a 100644
--- a/docs/source/installation.rst
+++ b/docs/source/installation.rst
@@ -13,12 +13,12 @@ the installation is in principle as simple as running
     pip install py-droplets
 
 
-In order to have all features of the package available, you might also want to 
+In order to have all features of the package available, you might also want to
 install the following optional packages:
 
 .. code-block:: bash
 
-	pip install h5py pyfftw
+    pip install h5py pyfftw
 
 
 Installing from source
@@ -35,8 +35,9 @@ The code builds on other python packages, which need to be installed for
 The required packages are listed in the table below:
 
 ===========  ========= =========
-Package      Version   Usage 
+Package      Version   Usage
 ===========  ========= =========
+h5py         >=2.10    Reading and writing data
 matplotlib   >=3.1     Visualizing results
 numpy        >=1.22    Array library used for storing data
 numba        >=0.59    Just-in-time compilation to accelerate numerics
@@ -53,7 +54,7 @@ latest version of the package.
 The `py-pde` package is available on `pip`, but if this is inconvenient the
 package can also be installed from github sources, as `described in its 
 documentation 
-<https://py-pde.readthedocs.io/en/latest/installation.html#installing-from-source>`_.  
+<https://py-pde.readthedocs.io/en/latest/installation.html#installing-from-source>`_
 
 A small subset of the package will only be available if extra optional packages are
 installed. Currently, this only concerns the `h5py` package for reading hdf files.
diff --git a/pyproject.toml b/pyproject.toml
index 83d8da9..8ee1786 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,6 +25,7 @@ classifiers = [
 
 # Requirements for setuptools
 dependencies = [
+    "h5py>=2.10",
     "matplotlib>=3.1",
     "numba>=0.59",
     "numpy>=1.22",
@@ -32,9 +33,6 @@ dependencies = [
     "py-pde>=0.37",
 ]
 
-[project.optional-dependencies]
-hdf = ["h5py>=2.10"]
-
 [project.urls]
 homepage = "https://github.com/zwicker-group/py-droplets"
 documentation = "http://py-droplets.readthedocs.io"
diff --git a/requirements.txt b/requirements.txt
index b419086..cefe2cd 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+h5py>=2.10
 matplotlib>=3.1
 numpy>=1.22
 numba>=0.59
diff --git a/tests/requirements.txt b/tests/requirements.txt
index bce7019..013776c 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,6 +1,5 @@
 -r ../requirements.txt
 black>=24.*
-h5py
 isort>=5.1
 pyupgrade>=3
 pytest>=5.4