diff --git a/travis-ci/managers/debian.sh b/travis-ci/managers/debian.sh
index a2a987d8fd..ab8a5b5fb8 100755
--- a/travis-ci/managers/debian.sh
+++ b/travis-ci/managers/debian.sh
@@ -59,8 +59,9 @@ for phase in "${PHASES[@]}"; do
         RUN|RUN_GCC|RUN_CLANG)
             if [[ "$phase" = "RUN_CLANG" ]]; then
                 ENV_VARS="-e CC=clang -e CXX=clang++"
+                MESON_ARGS="--optimization=1"
             fi
-            docker exec $ENV_VARS -it $CONT_NAME meson --werror -Dtests=unsafe -Dslow-tests=true -Dsplit-usr=true -Dman=true build
+            docker exec $ENV_VARS -it $CONT_NAME meson --werror -Dtests=unsafe -Dslow-tests=true -Dsplit-usr=true -Dman=true $MESON_ARGS build
             $DOCKER_EXEC ninja -v -C build
             docker exec -e "TRAVIS=$TRAVIS" -it $CONT_NAME ninja -C build test
             ;;