diff --git a/boards/sim/sim/sim/scripts/Make.defs b/boards/sim/sim/sim/scripts/Make.defs
index 686d2dd660..e501b6f340 100644
--- a/boards/sim/sim/sim/scripts/Make.defs
+++ b/boards/sim/sim/sim/scripts/Make.defs
@@ -79,8 +79,11 @@ endif
 
 ifeq ($(CONFIG_SIM_UBSAN),y)
   ARCHOPTIMIZATION += -fsanitize=undefined
-else ifeq ($(CONFIG_MM_UBSAN_ALL),y)
-  ARCHOPTIMIZATION += $(CONFIG_MM_UBSAN_OPTION)
+else
+  ifeq ($(CONFIG_MM_UBSAN_ALL),y)
+    ARCHOPTIMIZATION += $(CONFIG_MM_UBSAN_OPTION)
+  endif
+
   ifeq ($(CONFIG_MM_UBSAN_TRAP_ON_ERROR),y)
     ARCHOPTIMIZATION += -fsanitize-undefined-trap-on-error
   endif