diff --git a/README.md b/README.md
index e754469..e57e320 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,7 @@ If you're writing a highly-sophisticated command line tool, then `Boost.Program_
 ## TL;DR
 It doesn't get much simpler than this:
 ```cpp
+#include <iostream>
 #include "argh.h"
 
 int main(int, char* argv[])