diff --git a/packages/actstracking/package.py b/packages/actstracking/package.py
index bae8720..fbc6ef0 100644
--- a/packages/actstracking/package.py
+++ b/packages/actstracking/package.py
@@ -35,8 +35,8 @@ class Actstracking(CMakePackage, MCIlcsoftpackage):
     
     def setup_run_environment(self, spack_env):
         spack_env.prepend_path('MARLIN_DLL', self.prefix.lib + "/libACTSTracking.so")
-        spack_env.set("ACTS_TGeoFile", self.prefix.share.ACTSTracking.data + "MuColl_v1.root")
-        spack_env.set("ACTS_MatFile", self.prefix.share.ACTSTracking.data + "material-maps.json")
+        spack_env.set("ACTS_TGeoFile", self.prefix.share.ACTSTracking.data + "/MuColl_v1.root")
+        spack_env.set("ACTS_MatFile", self.prefix.share.ACTSTracking.data + "/material-maps.json")
 
     def cmake_args(self):
         # C++ Standard