diff --git a/pytransform3d/_array_api_compat.py b/pytransform3d/_array_api_compat.py
new file mode 100644
index 000000000..e985990e1
--- /dev/null
+++ b/pytransform3d/_array_api_compat.py
@@ -0,0 +1,9 @@
+import numpy as np
+
+
+def array_namespace(*args):
+    try:
+        import array_api_compat
+        return array_api_compat.array_namespace(*args)
+    except ImportError:
+        return np
diff --git a/pytransform3d/rotations/_utils.py b/pytransform3d/rotations/_utils.py
index dca93a2b2..047d9493e 100644
--- a/pytransform3d/rotations/_utils.py
+++ b/pytransform3d/rotations/_utils.py
@@ -1,9 +1,9 @@
 """Utility functions for rotations."""
 import warnings
 import math
-import array_api_compat
 import numpy as np
 from ._constants import unitz, eps, two_pi
+from .._array_api_compat import array_namespace
 
 
 def norm_vector(v):
@@ -19,7 +19,7 @@ def norm_vector(v):
     u : array, shape (n,)
         nd unit vector with norm 1 or the zero vector
     """
-    xp = array_api_compat.array_namespace(v)
+    xp = array_namespace(v)
 
     norm = xp.linalg.norm(v)
     if norm == 0.0:
diff --git a/setup.py b/setup.py
index 1e7984762..e7ea962a5 100644
--- a/setup.py
+++ b/setup.py
@@ -24,10 +24,10 @@
           ],
           license='BSD-3-Clause',
           packages=find_packages(),
-          install_requires=["numpy", "scipy", "matplotlib", "lxml",
-                            "array-api-compat"],
+          install_requires=["numpy", "scipy", "matplotlib", "lxml"],
           extras_require={
-              "all": ["pydot", "trimesh", "pycollada", "open3d"],
+              "all": ["pydot", "trimesh", "pycollada", "open3d",
+                      "array-api-compat"],
               "doc": ["numpydoc", "sphinx", "sphinx-gallery",
                       "sphinx-bootstrap-theme"],
               "test": ["pytest", "pytest-cov"]