diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 27ec669..63767e6 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -187,7 +187,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-22.04
+          # Firefox isn't available on 22.04 yet, so we must use 20.04
+          - os: ubuntu-20.04
             host: x86_64-unknown-linux-musl
           - os: windows-2022
             host: x86_64-pc-windows-msvc