diff --git a/.readthedocs.yml b/.readthedocs.yml
index 23bcdbc7..23c1c1ad 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -7,15 +7,20 @@ version: 2
 
 # Set the version of Python and other tools you might need
 build:
-  os: ubuntu-20.04
+  os: ubuntu-24.04
   tools:
-    python: "3.11"
+    python: "3.13"
+  jobs:
+    post_install:
+      # We just need to pass -config-settings, others are what RTD does by default.
+      - python -m pip install -upgrade-strategy only-if-needed --no-cache-dir -config-settings=setup-args="-Dbuild_extensions=false" .
 
 # Install the package.
 python:
   install:
     - method: pip
-      path: .
+      # Can't use path, want to disable meson building extensions.
+      # path: .
     - requirements: docs-requirements.txt
 
 # Build documentation in the docs/ directory with Sphinx
diff --git a/meson.build b/meson.build
index 9b84453a..2e983171 100644
--- a/meson.build
+++ b/meson.build
@@ -10,17 +10,7 @@ fs = import('fs')
 py = import('python').find_installation(pure: false)
 dep_py = py.dependency()
 
-build_extensions = get_option('build_extensions')
-summary({'option': build_extensions}, section: 'Build C Extensions')
-
-# Can't check environment variables directly, need to launch Python.
-res = run_command(py, '-c', 'import os; print("READTHEDOCS" in os.environ)', check: true)
-if res.returncode() == 0 and 'True' in res.stdout()
-  build_extensions = false
-endif
-summary({'stdout': res.stdout(), 'build': build_extensions}, section: 'Build C Extensions')
-
-if build_extensions
+if get_option('build_extensions')
     # Build quickhull.
     inc_quickhull = include_directories('src' / 'quickhull')
     lib_quickhull = static_library(
diff --git a/src/srctools/meson.build b/src/srctools/meson.build
index 62a31171..48bf780e 100644
--- a/src/srctools/meson.build
+++ b/src/srctools/meson.build
@@ -44,7 +44,7 @@ py.install_sources(pure_python, subdir: 'srctools')
 subdir('_pyinstaller')
 subdir('scripts')
 
-if build_extensions
+if get_option('build_extensions')
     py.extension_module(
         '_math',
         files(