diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e8b0ff5..7f99066 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -61,15 +61,15 @@ Initial setup:
 Build docs:
 
     # Linux
-    poetry run make -C doc html SPHINXOPTS=-tmain
+    poetry run make -C doc html
     xdg-open doc/main/build/html/index.html
 
     # macOS
-    poetry run make -C doc html SPHINXOPTS=-tmain
+    poetry run make -C doc html
     open doc/main/build/html/index.html
 
     # Windows (PowerShell)
-    poetry run doc\make.bat html SPHINXOPTS=-tmain
+    poetry run doc\make.bat html
     Invoke-Item doc\main\build\html\index.html
 
 Linting:
diff --git a/doc/Makefile b/doc/Makefile
index 82afe98..1aa579c 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -2,7 +2,7 @@
 #
 
 # You can set these variables from the command line.
-SPHINXOPTS    = -W
+SPHINXOPTS    = -W -tmain
 SPHINXBUILD   = sphinx-build
 SPHINXPROJ    = Pybricks
 SOURCEDIR     = main
diff --git a/doc/make.bat b/doc/make.bat
index eccd311..6f4581f 100644
--- a/doc/make.bat
+++ b/doc/make.bat
@@ -7,7 +7,7 @@ REM Command file for Sphinx documentation
 if "%SPHINXBUILD%" == "" (
 	set SPHINXBUILD=sphinx-build
 )
-set SPHINXOPTS=-W
+set SPHINXOPTS=-W -tmain
 set SOURCEDIR=main
 set BUILDDIR=%SOURCEDIR%/build
 set SPHINXPROJ=Pybricks