diff --git a/boards/sim/sim/sim/scripts/Make.defs b/boards/sim/sim/sim/scripts/Make.defs
index e0466796db1..9b31d9f73fd 100644
--- a/boards/sim/sim/sim/scripts/Make.defs
+++ b/boards/sim/sim/sim/scripts/Make.defs
@@ -78,7 +78,7 @@ OBJDUMP = $(CROSSDEV)objdump
 CFLAGS := $(ARCHWARNINGS) $(ARCHOPTIMIZATION) \
    $(ARCHCPUFLAGS) $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS) -pipe
 CXXFLAGS := $(ARCHWARNINGSXX) $(ARCHOPTIMIZATION) \
-   $(ARCHCPUFLAGSXX) $(ARCHXXINCLUDES) $(ARCHDEFINESXX) $(EXTRAFLAGS) -pipe
+   $(ARCHCPUFLAGSXX) $(ARCHXXINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS) -pipe
 CPPFLAGS := $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS)
 AFLAGS := $(CFLAGS) -D__ASSEMBLY__