diff --git a/site_scons/cc.scons b/site_scons/cc.scons
index 69e91a44e..507ec04a4 100644
--- a/site_scons/cc.scons
+++ b/site_scons/cc.scons
@@ -28,6 +28,7 @@ ENV.AppendUnique(
         "-Wbuiltin-declaration-mismatch",
         "-Wredundant-decls",
         "-Wdouble-promotion",
+        "-Wchar-subscripts",
         "-fdata-sections",
         "-ffunction-sections",
         "-fsingle-precision-constant",