diff --git a/pkgs/development/libraries/zlib/default.nix b/pkgs/development/libraries/zlib/default.nix
index 95c891e9bc7..df834f9f885 100644
--- a/pkgs/development/libraries/zlib/default.nix
+++ b/pkgs/development/libraries/zlib/default.nix
@@ -1,11 +1,13 @@
 {stdenv, fetchurl, static ? false}:
 
-stdenv.mkDerivation {
-  name = "zlib-1.2.3";
+stdenv.mkDerivation rec {
+  name = "zlib-1.2.5";
+  
   src = fetchurl {
-    url = http://www.zlib.net/zlib-1.2.3.tar.gz;
-    md5 = "debc62758716a169df9f62e6ab2bc634";
+    url = "http://www.zlib.net/${name}.tar.gz";
+    sha256 = "0n7rlgvjn73pyil3s1l6p77m7wkc809n934rnzxv1b1za4pfar30";
   };
+
   configureFlags = if static then "" else "--shared";
 
   preConfigure = ''