diff --git a/Dockerfile b/Dockerfile
index 071fc5c..6481a62 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,6 +12,9 @@ RUN dpkg -i /tmp/debsuryorg-archive-keyring.deb
 RUN sh -c 'echo "deb [signed-by=/usr/share/keyrings/deb.sury.org-php.gpg] https://packages.sury.org/php/ $(lsb_release -sc) main" > /etc/apt/sources.list.d/php.list'
 RUN apt update
 
+# install gpg
+RUN apt install -yqq gpg
+
 # install zip / unzip
 RUN apt install -yqq zip unzip