diff --git a/spack-environment/packages.yaml b/spack-environment/packages.yaml
index ce7959d22cadc522f1fcbc85d35071678868f082..a812e305777d2b62a54e8e4ef24e17db6bd186b6 100644
--- a/spack-environment/packages.yaml
+++ b/spack-environment/packages.yaml
@@ -112,6 +112,10 @@ packages:
     require:
     - '@12.1'
     - -debuginfod
+  g4ndl:
+    externals:
+    - spec: g4ndl@4.7
+      prefix: /opt/software/externals/g4ndl
   geant4:
     require:
     - '@11.1.2.east'