diff --git a/doc/build-unix.md b/doc/build-unix.md
index 9592c9391..92c7ada8e 100644
--- a/doc/build-unix.md
+++ b/doc/build-unix.md
@@ -82,6 +82,7 @@ install necessary parts of boost:
 BerkeleyDB is required for the wallet. db4.8 packages are available [here](https://launchpad.net/~bitcoin/+archive/bitcoin).
 You can add the repository and install using the following commands:
 
+    sudo apt-get install software-properties-common
     sudo add-apt-repository ppa:bitcoin/bitcoin
     sudo apt-get update
     sudo apt-get install libdb4.8-dev libdb4.8++-dev