diff --git a/boards/sim/sim/sim/scripts/Make.defs b/boards/sim/sim/sim/scripts/Make.defs
index 23b6acdcf34..663bef62ada 100644
--- a/boards/sim/sim/sim/scripts/Make.defs
+++ b/boards/sim/sim/sim/scripts/Make.defs
@@ -101,7 +101,15 @@ CPPFLAGS := $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS)
 AFLAGS := $(CFLAGS) -D__ASSEMBLY__
 
 ifeq ($(CONFIG_LIBCXX),y)
-  CXXFLAGS += -DLIBCXX_BUILDING_LIBCXXABI
+  ifeq ($(CONFIG_HOST_MACOS),y)
+    # macOS uses libc++abi
+    CXXFLAGS += -DLIBCXX_BUILDING_LIBCXXABI
+  else
+    # Linux C++ ABI seems vary.
+    # Probably __GLIBCXX__ is the best bet.
+    # XXX what to do for windows?
+    CXXFLAGS += -D__GLIBCXX__
+  endif
 endif
 
 # Loadable module definitions