diff --git a/Dockerfile b/Dockerfile
index 868d0b9..03ae44d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -29,7 +29,7 @@ ARG MDBOOK_GRAPHVIZ_VERSION=0.1.3
 ARG CARGO_ABOUT_VERSION=0.4.4
 ARG CARGO_AUDIT_VERSION=0.16.0
 ARG CARGO_DENY_VERSION=0.11.0
-ARG ZLIB_VERSION=1.2.11
+ARG ZLIB_VERSION=1.2.13
 ARG POSTGRESQL_VERSION=11.14
 
 # Make sure we have basic dev tools for building C libraries.  Our goal here is