diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index 96085e88..722d9f83 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -10,6 +10,7 @@ on:
 jobs:
   test-suite:
     strategy:
+      fail-fast: false
       matrix:
         os: [ 'ubuntu-latest' ] # , 'windows-latest', 'macos-latest' ]
         python_version: [ '3.9', '3.10', '3.11' ]
diff --git a/setup.sh b/setup.sh
index b1f75598..9433376b 100755
--- a/setup.sh
+++ b/setup.sh
@@ -19,6 +19,10 @@ tar xf firefox-102.2.0esr.source.tar.xz
 echo "Done downloading spidermonkey source code"
 
 echo "Building spidermonkey"
+cd firefox-102.2.0/python/mozbuild/mozbuild
+# the build system breaks on Python 3.11 (`io.open()` no longer accepts 'U' in the file mode)
+sed -i 's/"rU"/"r"/g' util.py preprocessor.py action/process_define_files.py backend/base.py
+cd -
 cd firefox-102.2.0/js
 sed -i 's/bool Unbox/JS_PUBLIC_API bool Unbox/g' ./public/Class.h           # need to manually add JS_PUBLIC_API to js::Unbox until it gets fixed in Spidermonkey
 sed -i 's/bool js::Unbox/JS_PUBLIC_API bool js::Unbox/g' ./src/vm/JSObject.cpp  # same here