1 files changed, 4 insertions, 2 deletions
diff --git a/pkgs/development/libraries/physics/geant4/g4py/default.nix b/pkgs/development/libraries/physics/geant4/g4py/default.nix
index dddd7078b86e..69fb5a99738a 100644
--- a/pkgs/development/libraries/physics/geant4/g4py/default.nix
+++ b/pkgs/development/libraries/physics/geant4/g4py/default.nix
@@ -18,13 +18,15 @@ stdenv.mkDerivation {
   inherit (geant4_nomt) version src;
   pname = "g4py";
 
-  sourceRoot = "geant4.10.05.p01/environments/g4py";
-
   nativeBuildInputs = [ cmake ];
   buildInputs = [ geant4_nomt xercesc boost_python python ];
 
   GEANT4_INSTALL = geant4_nomt;
 
+  postPatch = ''
+    cd environments/g4py
+  '';
+
   preConfigure = ''
     # Fix for boost 1.67+
     substituteInPlace CMakeLists.txt \