diff --git a/examples/lighting-app/silabs/openthread.gn b/examples/lighting-app/silabs/openthread.gn
index b05216fc9d7eae..acc23ef549aa3b 100644
--- a/examples/lighting-app/silabs/openthread.gn
+++ b/examples/lighting-app/silabs/openthread.gn
@@ -24,6 +24,7 @@ default_args = {
   target_cpu = "arm"
   target_os = "freertos"
   chip_openthread_ftd = true
+  optimize_debug_level = "s"
 
   import("//openthread.gni")
 }