diff --git a/signer_client.Dockerfile b/signer_client.Dockerfile
index b0d4ab3..663cd69 100644
--- a/signer_client.Dockerfile
+++ b/signer_client.Dockerfile
@@ -12,6 +12,7 @@ RUN apt-get update \
     libdbi-perl \
     libdevice-serialport-perl \
     libfile-counterfile-perl \
+    libreadonly-perl \
     openssl \
     perl \
     socat \