diff --git a/pkgs/by-name/zo/zookeeper/package.nix b/pkgs/by-name/zo/zookeeper/package.nix
index ad6c01e43717..e90cd30c6dde 100644
--- a/pkgs/by-name/zo/zookeeper/package.nix
+++ b/pkgs/by-name/zo/zookeeper/package.nix
@@ -15,7 +15,7 @@ let
 in
 stdenv.mkDerivation (finalAttrs: {
   pname = "zookeeper";
-  version = "3.9.5";
+  version = "3.9.5"; # Don't forget to update zookeeper_mt's hash!
 
   src = fetchurl {
     url = "mirror://apache/zookeeper/zookeeper-${finalAttrs.version}/apache-zookeeper-${finalAttrs.version}-bin.tar.gz";
diff --git a/pkgs/by-name/zo/zookeeper_mt/package.nix b/pkgs/by-name/zo/zookeeper_mt/package.nix
index e81724314499..44dc1fdf8cd8 100644
--- a/pkgs/by-name/zo/zookeeper_mt/package.nix
+++ b/pkgs/by-name/zo/zookeeper_mt/package.nix
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
 
   src = fetchurl {
     url = "mirror://apache/zookeeper/${zookeeper.pname}-${version}/apache-${zookeeper.pname}-${version}.tar.gz";
-    hash = "sha512-K8HvBwIdf0tHVotFoFuk0uYr2HFPsCKjPmK9xI/hHTxkpT1Tyx11Lxel9NlJppttillKMYAHvgrzinPDcQ7bdg==";
+    hash = "sha512-Zb6uvLbvf2m4RMLwpZ3E2S9ChFvcOpyp/TH+WSfTe6tOmecAnv/YM6gz4z5PyBulyg0j7jqc3BmQvotvyPt5tw==";
   };
 
   sourceRoot = "apache-${zookeeper.pname}-${version}/zookeeper-client/zookeeper-client-c";