diff --git a/README.md b/README.md
index 94ef06eb81..e7341cf6f8 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ You'll need these things to build the project:
  - Meson (`pip install meson`)
  - Clang and LLD (on mac, `brew install llvm`, on linux, `sudo apt install clang lld` or `sudo pacman -S clang lld` or whatever)
  - sqlite3 (this is so common it may already be installed on linux and is definitely already installed on mac. if not, do something like `sudo apt install libsqlite3-dev`)
+ - libarchive (`brew install libarchive`, `sudo port install libarchive`, `sudo apt install libarchive-dev`) TODO: bundle this dependency
 
 ## Build for iOS
 
@@ -40,7 +41,7 @@ Open the project in Xcode, open iSH.xcconfig, and change `ROOT_BUNDLE_IDENTIFIER
 
 To set up your environment, cd to the project and run `meson build` to create a build directory in `build`. Then cd to the build directory and run `ninja`.
 
-To set up a self-contained Alpine linux filesystem, download the Alpine minirootfs tarball for i386 from the [Alpine website](https://alpinelinux.org/downloads/) and run `./tools/fakefsify`, with the minirootfs tarball as the first argument and the name of the output directory as the second argument. Then you can run things inside the Alpine filesystem with `./ish -f alpine /bin/login -f root`, assuming the output directory is called `alpine`.
+To set up a self-contained Alpine linux filesystem, download the Alpine minirootfs tarball for i386 from the [Alpine website](https://alpinelinux.org/downloads/) and run `./tools/fakefsify`, with the minirootfs tarball as the first argument and the name of the output directory as the second argument. Then you can run things inside the Alpine filesystem with `./ish -f alpine /bin/login -f root`, assuming the output directory is called `alpine`. If `tools/fakefsify` doesn't exist for you in your build directory, that might be because it couldn't find libarchive on your system (see above for ways to install it.)
 
 You can replace `ish` with `tools/ptraceomatic` to run the program in a real process and single step and compare the registers at each step. I use it for debugging. Requires 64-bit Linux 4.11 or later.