diff --git a/install_spack_env.sh b/install_spack_env.sh
index f0065f9888b9bfb93d811e327ce12627d5b49ec4..536696f8a4fa342bad3f9975bc2ff57f96d62add 100644
--- a/install_spack_env.sh
+++ b/install_spack_env.sh
@@ -80,7 +80,7 @@ spack env activate $EBRAINS_SPACK_ENV
 
 # fetch all sources
 spack concretize --fresh --test root
-spack fetch --dependencies --missing
+spack-python -c "exit(not len(spack.environment.active_environment().uninstalled_specs()))" && spack fetch --dependencies --missing
 rm $SPACK_ROOT/var/spack/environments/$EBRAINS_SPACK_ENV/spack.lock
 
 # install the environment, use 2 jobs to reduce the amount of required RAM