diff --git a/etc/ci/buildbot_steps.yml b/etc/ci/buildbot_steps.yml
index 62ba5177841d..0c977c38700b 100644
--- a/etc/ci/buildbot_steps.yml
+++ b/etc/ci/buildbot_steps.yml
@@ -72,7 +72,7 @@ linux-rel-nogate:
   - ./mach clean-nightlies --keep 3 --force
   - env CC=gcc-5 CXX=g++-5 ./mach build --release
   - python ./etc/ci/chaos_monkey_test.py
-  - env CC=gcc-5 CXX=g++-5 bash ./etc/ci/mutation_test.sh
+  - env CC=gcc-5 CXX=g++-5 RUSTFLAGS= bash ./etc/ci/mutation_test.sh
 
 mac-rel-intermittent:
   - ./mach clean-nightlies --keep 3 --force