diff --git a/.readthedocs.yml b/.readthedocs.yml
index cafcedd..71d5df4 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -3,6 +3,8 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.11"
+  apt_packages:
+    - r-base-core
 python:
   install:
     - method: pip
@@ -10,4 +12,5 @@ python:
       extra_requirements:
         - doc
 sphinx:
+  fail_on_warning: true
   configuration: docs/conf.py
diff --git a/docs/conf.py b/docs/conf.py
index 4be7543..db3b00b 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,41 +1,16 @@
 """Sphinx configuration."""
 
 import sys
-from abc import ABC
 from datetime import datetime, timezone
 from importlib.metadata import metadata
 from pathlib import Path
-from unittest.mock import MagicMock, patch
-
-
-def mock_rpy2() -> None:
-    """Can’t use autodoc_mock_imports as we import anndata2ri."""
-    patch('rpy2.situation.get_r_home', lambda: None).start()
-    sys.modules['rpy2.rinterface_lib'] = MagicMock()
-    submods = ['embedded', 'conversion', 'memorymanagement', 'sexp', 'bufferprotocol', 'callbacks', '_rinterface_capi']
-    sys.modules.update({f'rpy2.rinterface_lib.{sub}': MagicMock() for sub in submods})
-    sexp = sys.modules['rpy2.rinterface_lib'].sexp = sys.modules['rpy2.rinterface_lib.sexp']
-    sexp.Sexp = type('Sexp', (MagicMock, ABC), dict(__module__='rpy2.rinterface_lib.sexp'))
-    sexp.SexpEnvironment = type('SexpEnvironment', (sexp.Sexp,), dict(__module__='rpy2.rinterface_lib.sexp'))
-    sexp.SexpVector = sexp.StrSexpVector = MagicMock
-    sexp.SexpVector.from_iterable = MagicMock()
-
-    import rpy2.rinterface
-    import rpy2.rinterface_lib.sexp
-
-    rpy2.rinterface_lib = sys.modules['rpy2.rinterface_lib']
-    rpy2.rinterface._MissingArgType = object  # noqa: SLF001
-    rpy2.rinterface.initr_simple = lambda *_, **__: None
-
-    assert rpy2.rinterface_lib.sexp is sexp
 
 
 HERE = Path(__file__).parent
 
-mock_rpy2()
 
-# now we can anndata2ri and our extensions
-sys.path[:0] = [str(HERE.parent), str(HERE / 'ext')]
+# allow to import our extensions
+sys.path[:0] = [str(HERE / 'ext')]
 
 
 # -- General configuration ------------------------------------------------