diff --git a/boards/sim/sim/sim/scripts/Make.defs b/boards/sim/sim/sim/scripts/Make.defs
index be3fc1f763c..c8897d9fb9e 100644
--- a/boards/sim/sim/sim/scripts/Make.defs
+++ b/boards/sim/sim/sim/scripts/Make.defs
@@ -122,6 +122,14 @@ ifeq ($(CONFIG_LIBCXX),y)
     # XXX what to do for windows?
     CXXFLAGS += -D__GLIBCXX__
   endif
+
+  # Disable availability macros.
+  # The availability on Host OS is not likely appropriate for NuttX.
+  #
+  # Note: When compiling NuttX apps, we undefine __APPLE__.
+  # It makes libcxx __availability header unhappy.
+  # https://github.com/llvm/llvm-project/blob/2e2999cd44f6ec9a5e396fa0113497ea82582f69/libcxx/include/__availability#L258
+  CXXFLAGS += -D_LIBCPP_DISABLE_AVAILABILITY
 endif
 
 ifeq ($(CONFIG_SIM_ASAN),y)