diff --git a/src/xfel_calibrate/calibrate.py b/src/xfel_calibrate/calibrate.py
index 5d2b63c6f4d00a2e717bd86cd95c37e5b56b2a0c..00e1318063e002acd1d2cbc597decedcdcfccd37 100755
--- a/src/xfel_calibrate/calibrate.py
+++ b/src/xfel_calibrate/calibrate.py
@@ -715,6 +715,8 @@ def run(argv=None):
     # Record installed Python packages for reproducing the environment
     if not args['skip_env_freeze']:
         with (cal_work_dir / 'requirements.txt').open('wb') as f:
+            print('--index-url https://devpi.exfldadev01.desy.de/euxfel/internal',
+                  file=f, flush=True)
             check_call([python_exe, '-m', 'pip', 'freeze'], stdout=f)
 
     folder = get_par_attr(parms, 'in_folder', 'value', '')