diff --git a/README.md b/README.md
index 86c227b..f781bd8 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,6 @@ Custom firmware USB device: 1CCF:2333
 ```
 $ git clone ...
 $ git submodule update --init
-$ zig build -Drelease-fast=true
+$ zig build -Drelease-safe=true
 $ ls zig-out/lib/chuniio_tasoller.dll
 ```