diff --git a/pkgs/applications/science/chemistry/gwyddion/default.nix b/pkgs/applications/science/chemistry/gwyddion/default.nix
index 4f028e0053af..6ea6be52fce4 100644
--- a/pkgs/applications/science/chemistry/gwyddion/default.nix
+++ b/pkgs/applications/science/chemistry/gwyddion/default.nix
@@ -2,11 +2,11 @@
 
 with stdenv.lib;
 
+let version = "2.48"; in
 stdenv.mkDerivation {
   name = "gwyddion-${version}";
-  version = "2.48";
   src = fetchurl {
-    url = "http://sourceforge.net/projects/gwyddion/files/gwyddion/2.48/gwyddion-2.48.tar.xz";
+    url = "http://sourceforge.net/projects/gwyddion/files/gwyddion/${version}/gwyddion-${version}.tar.xz";
     sha256 = "119iw58ac2wn4cas6js8m7r1n4gmmkga6b1y711xzcyjp9hshgwx";
   };
   nativeBuildInputs = [ pkgconfig ];
diff --git a/pkgs/applications/science/math/ripser/default.nix b/pkgs/applications/science/math/ripser/default.nix
index 651ad8a2c0f8..21948a279d07 100644
--- a/pkgs/applications/science/math/ripser/default.nix
+++ b/pkgs/applications/science/math/ripser/default.nix
@@ -13,10 +13,10 @@ assert useGoogleHashmap -> sparsehash != null;
 
 let
   inherit (stdenv.lib) optional;
+  version = "1.0";
 in
 stdenv.mkDerivation {
   name = "ripser-${version}";
-  version = "1.0";
 
   src = fetchFromGitHub {
     owner = "Ripser";