diff --git a/etc/ci/buildbot_steps.yml b/etc/ci/buildbot_steps.yml
index c3b413742f3..586732df875 100644
--- a/etc/ci/buildbot_steps.yml
+++ b/etc/ci/buildbot_steps.yml
@@ -2,7 +2,7 @@ mac-rel-wpt1:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach build --release
   - ./mach test-wpt-failure
-  - ./mach test-wpt --release --processes 8 --total-chunks 2 --this-chunk 1 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
+  - ./mach test-wpt --release --processes 4 --total-chunks 2 --this-chunk 1 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
   - ./mach filter-intermittents wpt-errorsummary.log --log-intermittents intermittents.log --log-filteredsummary filtered-wpt-errorsummary.log --use-tracker
   - ./mach test-wpt --release --binary-arg=--multiprocess --processes 8 --log-raw test-wpt-mp.log --log-errorsummary wpt-mp-errorsummary.log eventsource
   - ./mach build-cef --release
@@ -12,7 +12,7 @@ mac-rel-wpt1:
 mac-rel-wpt2:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach build --release
-  - ./mach test-wpt --release --processes 8 --total-chunks 2 --this-chunk 2 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
+  - ./mach test-wpt --release --processes 4 --total-chunks 2 --this-chunk 2 --log-raw test-wpt.log --log-errorsummary wpt-errorsummary.log --always-succeed
   - ./mach filter-intermittents wpt-errorsummary.log --log-intermittents intermittents.log --log-filteredsummary filtered-wpt-errorsummary.log --use-tracker
   - ./mach build-geckolib --release