diff --git a/pkgs/build-support/fetchgit/nix-prefetch-git b/pkgs/build-support/fetchgit/nix-prefetch-git
index 931be1a37007..8020ba46f3f1 100755
--- a/pkgs/build-support/fetchgit/nix-prefetch-git
+++ b/pkgs/build-support/fetchgit/nix-prefetch-git
@@ -42,6 +42,7 @@ Options:
       --url url       Any url understood by 'git clone'.
       --rev ref       Any sha1 or references (such as refs/heads/master)
       --hash h        Expected hash.
+      --branch-name   Branch name to check out into
       --deepClone     Clone the entire repository.
       --no-deepClone  Make a shallow clone of just the required ref.
       --leave-dotGit  Keep the .git directories.