diff --git a/README.md b/README.md
index 4e01bf4f5..305cf31c4 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,7 @@ Best supported on Ubuntu 14.04 with default `gdb` or `gdb-multiarch` (e.g. with
 As of changes made May 17 you must have GDB 7.9 or newer.  Ubuntu Vivid users already have this.  Otherwise, you'll have to build it from source.  This works for Ubuntu 14.04:
 
 ```sh
+$ sudo apt-get build-dep gdb
 $ wget http://archive.ubuntu.com/ubuntu/pool/main/g/gdb/gdb_7.9.orig.tar.gz
 $ tar xf gdb_7.9.orig.tar.gz
 $ cd gdb-7.9