diff --git a/etc/ci/buildbot_steps.yml b/etc/ci/buildbot_steps.yml
index 2b8e84638b2..0b70fcff4f5 100644
--- a/etc/ci/buildbot_steps.yml
+++ b/etc/ci/buildbot_steps.yml
@@ -74,6 +74,10 @@ mac-nightly:
   - ./etc/ci/update-wpt-checkout cleanup
 
 linux-rel-intermittent:
+ env:
+   CC: gcc-5
+   CXX: g++-5
+ commands:
   - ./mach clean-nightlies --keep 3 --force
   - ./mach clean-cargo-cache --keep 3 --force
   - ./etc/ci/clean_build_artifacts.sh