diff --git a/example_designs/make.py b/example_designs/make.py
index f8be1d9..1266a38 100644
--- a/example_designs/make.py
+++ b/example_designs/make.py
@@ -91,7 +91,7 @@ if __name__ == "__main__":
         platform_kwargs = dict((k, autotype(v)) for k, v in args.platform_option)
         platform = platform_module.Platform(**platform_kwargs)
 
-    build_name = top_class.__name__.lower() + "-" + platform_name
+    build_name = top_class.__name__.lower() + "_" + platform_name
     top_kwargs = dict((k, autotype(v)) for k, v in args.target_option)
     soc = top_class(platform, **top_kwargs)
     soc.finalize()