diff --git a/virtme_ng/run.py b/virtme_ng/run.py
index 6c3237a..f7cd82d 100644
--- a/virtme_ng/run.py
+++ b/virtme_ng/run.py
@@ -596,6 +596,7 @@ def arg_fail(message, show_usage=True):
         "kernel_target": "Image",
         "kernel_image": "Image",
     },
+    # adding a new arch? Please also update get_host_arch().
 }
 
 MAKE_COMMAND = "make LOCALVERSION=-virtme"
@@ -911,7 +912,7 @@ def _get_virtme_user(self, args):
     def _get_virtme_arch(self, args):
         if args.arch is not None:
             if args.arch not in ARCH_MAPPING:
-                arg_fail(f"unsupported architecture: {args.arch}")
+                arg_fail(f"unsupported architecture, available: {" ".join(ARCH_MAPPING)}")
             if args.root is None and get_host_arch() != args.arch:
                 arg_fail("--arch used without --root")
             if "max-cpus" in ARCH_MAPPING[args.arch]: