diff --git a/Tools/ardupilotwaf/boards.py b/Tools/ardupilotwaf/boards.py
index 5131087ce9..8ccb521498 100644
--- a/Tools/ardupilotwaf/boards.py
+++ b/Tools/ardupilotwaf/boards.py
@@ -653,7 +653,8 @@ class sitl(Board):
                                 CANARD_ENABLE_CANFD = 1)
 
         env.CXXFLAGS += [
-            '-Werror=float-equal'
+            '-Werror=float-equal',
+            '-Werror=missing-declarations',
         ]
 
         if cfg.options.ubsan or cfg.options.ubsan_abort: