diff --git a/scripts/dns.sh b/scripts/dns.sh
index bad17086..d0a2d310 100644
--- a/scripts/dns.sh
+++ b/scripts/dns.sh
@@ -21,8 +21,9 @@ else
 fi
 
 # Okay now install the package.
+# bc is needed by dns_update.
 
-apt_install nsd
+apt_install nsd bc
 
 # Prepare nsd's configuration.