diff --git a/pkgs/applications/science/biology/ncbi-tools/default.nix b/pkgs/applications/science/biology/ncbi-tools/default.nix
index 43dc25d13fb0..45460c4b1aa9 100644
--- a/pkgs/applications/science/biology/ncbi-tools/default.nix
+++ b/pkgs/applications/science/biology/ncbi-tools/default.nix
@@ -18,5 +18,6 @@ stdenv.mkDerivation rec {
     longDescription = ''The NCBI Bioinformatics toolsbox, including command-line utilties, libraries and include files. No X11 support (at this point).'';
     homepage = http://www.ncbi.nlm.nih.gov/IEB/ToolBox/; 
     license = "GPL";
+    priority = "5";   # zlib.so gives a conflict with zlib
   };
 }