diff --git a/share/machdeps/make_machdep/make_machdep.py b/share/machdeps/make_machdep/make_machdep.py
index 8c8953f3be45d39705021088fe75712d5a40e748..6eb4fa52bb10df7ba1f0679d4e2fbb996bc86efe 100755
--- a/share/machdeps/make_machdep/make_machdep.py
+++ b/share/machdeps/make_machdep/make_machdep.py
@@ -99,6 +99,9 @@ args, other_args = parser.parse_known_args()
 if not args.compiler_flags:
     args.compiler_flags = ["-c"]
 
+if not args.cpp_arch_flags:
+    args.cpp_arch_flags = []
+
 
 def make_schema():
     schema_filename = my_path.parent / "machdep-schema.yaml"