diff --git a/docs/install.md b/docs/install.md
index ef14f5d84..16892c82f 100644
--- a/docs/install.md
+++ b/docs/install.md
@@ -27,7 +27,7 @@ rustup component add clippy
 # Install helper tools used by the workspace justfile:
 cargo install just
 # Optional: install nextest for the `just test` helper
-cargo install cargo-nextest
+cargo install --locked cargo-nextest
 
 # Build Codex.
 cargo build