diff --git a/signal/Dockerfile b/signal/Dockerfile
index 3168d6d..9ba7f5c 100644
--- a/signal/Dockerfile
+++ b/signal/Dockerfile
@@ -1,4 +1,4 @@
-FROM debian
+FROM debian:11.5
 RUN apt -y update
 RUN apt install -y curl gpg
 RUN curl -s https://updates.signal.org/desktop/apt/keys.asc | apt-key add -