diff --git a/README.md b/README.md
index cdae23b..3bc6df8 100644
--- a/README.md
+++ b/README.md
@@ -81,6 +81,8 @@ variables:
   locally configured SSH/git credentials)
 * `NIXERY_PKGS_PATH`: A local filesystem path containing a Nix package set to use
   for building
+* `NIX_TIMEOUT`: Number of seconds that any Nix builder is allowed to run
+  (defaults to 60
 * `GCS_SIGNING_KEY`: A Google service account key (in PEM format) that can be
   used to sign Cloud Storage URLs
 * `GCS_SIGNING_ACCOUNT`: Google service account ID that the signing key belongs
diff --git a/docs/src/run-your-own.md b/docs/src/run-your-own.md
index 0539ab0..7a294f5 100644
--- a/docs/src/run-your-own.md
+++ b/docs/src/run-your-own.md
@@ -81,8 +81,10 @@ You may set *one* of these, if unset Nixery defaults to `nixos-19.03`:
 * `NIXERY_PKGS_PATH`: A local filesystem path containing a Nix package set to use
   for building
 
-You may set *both* of these:
+You may set *all* of these:
 
+* `NIX_TIMEOUT`: Number of seconds that any Nix builder is allowed to run
+  (defaults to 60)
 * `GCS_SIGNING_KEY`: A Google service account key (in PEM format) that can be
   used to [sign Cloud Storage URLs][signed-urls]
 * `GCS_SIGNING_ACCOUNT`: Google service account ID that the signing key belongs