diff --git a/pkgs/servers/search/sphinxsearch/default.nix b/pkgs/servers/search/sphinxsearch/default.nix
index 040dace69fb..1979da5b2c0 100644
--- a/pkgs/servers/search/sphinxsearch/default.nix
+++ b/pkgs/servers/search/sphinxsearch/default.nix
@@ -1,6 +1,6 @@
 { stdenv, fetchurl, pkgconfig, mysql,
-  version = "2.1.9";
-  mainSrc = fetchurl {
+  version ? "2.1.9",
+  mainSrc ? fetchurl {
     url = "http://sphinxsearch.com/files/sphinx-${version}-release.tar.gz";
     sha256 = "00vwxf3zr0g1fq9mls1z2rd8nxw74b76pkl1j466lig1qc5am2b2";
   }