diff --git a/mix.exs b/mix.exs
index 05ff30af..93d80c69 100644
--- a/mix.exs
+++ b/mix.exs
@@ -10,7 +10,13 @@ defmodule Towerops.MixProject do
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
       deps: deps(),
-      compilers: [:towerops_nif, :phoenix_live_view] ++ Mix.compilers(),
+      # NIF compiled by `make -C c_src` in dev shell (nix/shell.nix) and
+      # pre-built by `towerops-nif` Nix package in CI/prod. Not an auto-compiler
+      # because Mix.Tasks.Compile.ToweropsNif is part of the project source and
+      # isn't available on the code path when Mix first resolves the compilers
+      # list in a fresh build. Run `mix compile.towerops_nif` manually when
+      # changing C source between `mix compile` runs in dev.
+      compilers: [:phoenix_live_view] ++ Mix.compilers(),
       prune_code_paths: false,
       listeners: [Phoenix.CodeReloader],
       dialyzer: dialyzer(),