diff --git a/.travis.yml b/.travis.yml
index 1e9837869508ed8c80d59a46ad32e693ccb9f370..f6aec9677083f4f23cf18cb712995f8870303ea1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -389,7 +389,7 @@ matrix:
       env:
         - TEST_PY_BD="sandbox"
           BUILDMAN="^sandbox$"
-          OVERRIDE="clang-7"
+          OVERRIDE="-O clang-7"
     - name: "test/py sandbox_spl"
       env:
         - TEST_PY_BD="sandbox_spl"