diff --git a/Dockerfile b/Dockerfile
index 0214040..24f12f3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,7 +7,7 @@ ENV LC_ALL C.UTF-8
 RUN apt-get -qqqy update
 RUN apt-get -qqqy install apt-utils software-properties-common dctrl-tools
 
-ARG DEB_VERSION=1:9.16.20-2+ubuntu21.04.1+isc+1
+ARG DEB_VERSION=1:9.16.20-2+ubuntu20.04.1+isc+1
 RUN add-apt-repository -y ppa:isc/bind
 RUN apt-get -qqqy update && apt-get -qqqy dist-upgrade && apt-get -qqqy install bind9=$DEB_VERSION bind9-utils=$DEB_VERSION