diff --git a/INSTALL.debian b/INSTALL.debian
index f0dac4dbce..aa53f6a5c2 100644
--- a/INSTALL.debian
+++ b/INSTALL.debian
@@ -31,7 +31,7 @@ Edit your /etc/apt/sources.list file and add the following:
 
 The Index Data packages are signed with a key you can install as follows:
 
-    $ wget -O- http://ftp.indexdata.dk/debian/indexdata.asc | sudo apt-key add
+    $ wget -O- http://ftp.indexdata.dk/debian/indexdata.asc | sudo apt-key add -
 
 Finally, update your apt sources:
     $ sudo apt-get update