diff --git a/readme.md b/readme.md
index 18cc5a9..fb90530 100755
--- a/readme.md
+++ b/readme.md
@@ -30,12 +30,18 @@ Currently ported to OS X, Linux and Windows. Tested on:
 
 ## Ubuntu
 
+The g++ compiler is required to build the native library. Generally this is already installed.
+
 You need to install the `libncurses5-dev` package to pick up the ncurses header files. Also worth installing the `ncurses-doc` package too.
 
 ## Windows
 
 You need to install Visual studio, and build from a Visual studio command prompt.
 
+## OS X
+
+The g++ compiler is required to build the native library. You will need to install the XCode tools.
+
 # TODO
 
 * Fix TERM=dumb