diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e0f80aaaa..c395f3e1c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -383,7 +383,7 @@ jobs:
       # Run Complement
       - run: |
           set -o pipefail
-          go test -v -json -tags synapse_blacklist,msc2403 ./tests/... 2>&1 | gotestfmt
+          go test -v -json -p 1 -tags synapse_blacklist,msc2403 ./tests/... 2>&1 | gotestfmt
         shell: bash
         name: Run Complement Tests
         env:
diff --git a/changelog.d/11910.misc b/changelog.d/11910.misc
new file mode 100644
index 000000000..d05130969
--- /dev/null
+++ b/changelog.d/11910.misc
@@ -0,0 +1 @@
+Run Complement tests sequentially.