diff --git a/.circleci/config.yml b/.circleci/config.yml
index 3ac2882..17a6e7e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -8,7 +8,7 @@ commands:
         type: string
       sphinx-version:
         type: string
-        default: "21,22,23,24,30,31,32,33,34,latest"
+        default: "21,22,23,24,30,31,32,33,34,35,40,41,42,43,44,latest"
     steps:
       - checkout
       - run: pip install --user tox
@@ -48,6 +48,13 @@ jobs:
       - run-tox:
           version: py39
 
+  py310:
+    docker:
+      - image: 'cimg/python:3.10'
+    steps:
+      - run-tox:
+          version: py310
+
   lint:
     docker:
       - image: 'cimg/python:3.9'
@@ -61,6 +68,7 @@ workflows:
   tests:
     jobs:
       - lint
+      - py310
       - py39
       - py38
       - py37
diff --git a/readthedocs_ext/readthedocs.py b/readthedocs_ext/readthedocs.py
index aac53a2..87efccf 100644
--- a/readthedocs_ext/readthedocs.py
+++ b/readthedocs_ext/readthedocs.py
@@ -249,9 +249,12 @@ def remove_search_init(app, exception):
         replacement_text = '/* Search initialization removed for Read the Docs */'
         replacement_regex = re.compile(
             r'''
-            ^\$\(document\).ready\(function\s*\(\)\s*{(?:\n|\r\n?)
+            ^(\$\(document\).ready\(function\s*\(\)\s*{(?:\n|\r\n?)
             \s*Search.init\(\);(?:\n|\r\n?)
-            \}\);
+            \}\);)
+            |
+            # Sphinx >=5.0 calls Search.init this way.
+            (_ready\(Search.init\);)
             ''',
             (re.MULTILINE | re.VERBOSE)
         )
diff --git a/tests/pr-example/conf.py b/tests/pr-example/conf.py
index 64f9361..cba627e 100644
--- a/tests/pr-example/conf.py
+++ b/tests/pr-example/conf.py
@@ -14,7 +14,7 @@
 author = 'readthedocs'
 version = '0.1'
 release = '0.1'
-language = None
+language = 'en'
 exclude_patterns = ['_build']
 todo_include_todos = False
 html_theme = 'alabaster'
diff --git a/tests/pyexample-json/conf.py b/tests/pyexample-json/conf.py
index 4916bbc..57fc48b 100644
--- a/tests/pyexample-json/conf.py
+++ b/tests/pyexample-json/conf.py
@@ -15,7 +15,7 @@
 author = u'readthedocs'
 version = '0.1'
 release = '0.1'
-language = None
+language = 'en'
 exclude_patterns = ['_build']
 pygments_style = 'sphinx'
 todo_include_todos = False
diff --git a/tests/pyexample/conf.py b/tests/pyexample/conf.py
index f566e4d..342bb69 100644
--- a/tests/pyexample/conf.py
+++ b/tests/pyexample/conf.py
@@ -15,7 +15,7 @@
 author = u'readthedocs'
 version = '0.1'
 release = '0.1'
-language = None
+language = 'en'
 exclude_patterns = ['_build']
 pygments_style = 'sphinx'
 todo_include_todos = False
diff --git a/tox.ini b/tox.ini
index 27c73ae..ebeb1bc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,7 @@
 [tox]
 envlist =
     py{27,36}-sphinx{15,16,17,18}
-    py{36,37,38,39}-sphinx{21,22,23,24,30,31,32,33,34,latest}
+    py{36,37,38,39,310}-sphinx{21,22,23,24,30,31,32,33,34,35,40,41,42,43,44,latest}
     lint
 
 [testenv]
@@ -24,7 +24,14 @@ deps =
     sphinx32: Sphinx<3.3
     sphinx33: Sphinx<3.4
     sphinx34: Sphinx<3.5
+    sphinx35: Sphinx<3.6
+    sphinx40: Sphinx<4.1
+    sphinx41: Sphinx<4.2
+    sphinx42: Sphinx<4.3
+    sphinx43: Sphinx<4.4
+    sphinx44: Sphinx<4.5
     sphinxlatest: Sphinx
+    sphinxmaster: git+https://github.com/sphinx-doc/sphinx.git@master
 commands =
     py.test {posargs}