diff --git a/calorimeters/run_simulation_zdc.sh b/calorimeters/run_simulation_zdc.sh
index 982fd37aff0a810e478e553902076a307740f7b2..fae6497ab3a3f5658a709a0bb7f6419d87836f27 100755
--- a/calorimeters/run_simulation_zdc.sh
+++ b/calorimeters/run_simulation_zdc.sh
@@ -1,5 +1,7 @@
 #!/bin/bash
 
+source /usr/local/bin/thisdd4hep.sh
+
 ddsim --runType batch --numberOfEvents 100 \
       --compactFile ./ZDC_example.xml \
       --inputFiles  ./data/zdc_photons.hepmc \