diff --git a/Makefile b/Makefile
index 65191b7..7552ba5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 SLUG = Fundamental
 VERSION = 0.5.1
 
-SOURCES = $(wildcard src/*.cpp)
+SOURCES += $(wildcard src/*.cpp)
 
 DISTRIBUTABLES += $(wildcard LICENSE*) res
 
diff --git a/README.md b/README.md
index b290386..3986a93 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,12 @@
 The Fundamental plugin pack gives you a basic foundation to create simple synthesizers, route and analyze signals, complement other more complicated modules, and build some not-so-simple patches using brute force (lots of modules).
 They are also a great reference for creating your own plugins in C++.
 
+## Building
+
+Follow the build instructions for [VCV Rack](https://github.com/VCVRack/Rack).
+The `master` branch of this repo builds against the `master` branch of Rack.
+To build for a previous version, use `git tag` to find a compatible version and `git checkout [TAG]` to check out the source for that version.
+
 ## License
 
 Source code licensed under [BSD-3-Clause](LICENSE.txt) by [Andrew Belt](https://andrewbelt.name/)