diff --git a/README.md b/README.md
index b51aaeb71..f7494ecbb 100644
--- a/README.md
+++ b/README.md
@@ -81,6 +81,10 @@ You can cross compile by setting `-Dtarget=<target-triple>`. For example,
 `zig build -Dtarget=aarch64-macos` will build for Apple Silicon macOS. Note
 that not all targets supported by Zig are supported.
 
+**Note: Zig nightly is required.** Ghostty is built against the nightly
+releases of Zig. The latest released version (0.9.1 at the time of this
+edit) will NOT work.
+
 Other useful commands:
 
   * `zig build test` for running unit tests.