diff --git a/Documentation/hacking.md b/Documentation/hacking.md
index 601688c..7f98b3d 100644
--- a/Documentation/hacking.md
+++ b/Documentation/hacking.md
@@ -8,6 +8,7 @@
   * cpio
   * squashfs-tools
   * realpath
+  * gpg
 * Go 1.3+
   * jteeuwen/go-bindata