diff --git a/pkgs/development/python-modules/sphinx-rtd-theme/default.nix b/pkgs/development/python-modules/sphinx-rtd-theme/default.nix
index 791f0b691d98..64db324635a0 100644
--- a/pkgs/development/python-modules/sphinx-rtd-theme/default.nix
+++ b/pkgs/development/python-modules/sphinx-rtd-theme/default.nix
@@ -2,9 +2,9 @@
   lib,
   buildPythonPackage,
   fetchPypi,
+  setuptools,
   docutils,
   sphinx,
-  readthedocs-sphinx-ext,
   sphinxcontrib-jquery,
   pytestCheckHook,
 }:
@@ -12,7 +12,7 @@
 buildPythonPackage rec {
   pname = "sphinx-rtd-theme";
   version = "3.0.2";
-  format = "setuptools";
+  pyproject = true;
 
   src = fetchPypi {
     pname = "sphinx_rtd_theme";
@@ -20,20 +20,28 @@ buildPythonPackage rec {
     hash = "sha256-t0V7wl3acjsgsIamcLmVPIWeq2CioD7o6yuyPhduX4U=";
   };
 
+  build-system = [ setuptools ];
+
   preBuild = ''
     # Don't use NPM to fetch assets. Assets are included in sdist.
     export CI=1
   '';
 
-  propagatedBuildInputs = [
+  dependencies = [
     docutils
     sphinx
     sphinxcontrib-jquery
   ];
 
+  pythonRelaxDeps = [
+    "docutils"
+    "sphinxcontrib-jquery"
+    # https://github.com/readthedocs/sphinx_rtd_theme/pull/1666
+    "sphinx"
+  ];
+
   nativeCheckInputs = [
     pytestCheckHook
-    readthedocs-sphinx-ext
   ];
 
   disabledTests = [
@@ -41,11 +49,6 @@ buildPythonPackage rec {
     "test_basic"
   ];
 
-  pythonRelaxDeps = [
-    "docutils"
-    "sphinxcontrib-jquery"
-  ];
-
   pythonImportsCheck = [ "sphinx_rtd_theme" ];
 
   meta = {