diff --git a/config/runtime/tests/rt-tests.jinja2 b/config/runtime/tests/rt-tests.jinja2
index 2d791f4449..203c7699a1 100644
--- a/config/runtime/tests/rt-tests.jinja2
+++ b/config/runtime/tests/rt-tests.jinja2
@@ -25,7 +25,7 @@
         PRIORITY: {{ priority|default('98') }}
         THREADS: {{ threads|default('2') }}
       {% elif tst_cmd == 'pi-stress' %}
-        MLOCKALL: {{ mlockall|default("true") }}
+        MLOCKALL: {{ mlockall|default('"true"') }}
       {% elif tst_cmd == 'rt-migrate-test' %}
         PRIORITY: {{ priority|default('90') }}
       {% elif tst_cmd == 'signaltest' %}